Solve the differential equation `(dy)/(dx) = -x sqrt(4-y^2)` given that `y(2) = 0`. Give your answer in the form `y = f(x)`. (3 marks)
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Solve the differential equation `(dy)/(dx) = -x sqrt(4-y^2)` given that `y(2) = 0`. Give your answer in the form `y = f(x)`. (3 marks)
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`y=2sin(-(1)/(2)x^(2)+2)`
| `int(dy)/(sqrt(4-y^(2)))` | `=int-x\ dx` | |
| `sin^(-1)((y)/(2))` | `=-(1)/(2)x^(2)+c` |
`y(2)=0\ \=> \ c=2`
| `(y)/(2)` | `=sin(-(1)/(2)x^(2)+2)` | |
| `y` | `=2sin(-(1)/(2)x^(2)+2)` |
The points with coordinates \(A(1,1,2), B(1,2,3)\) and \(C(3,2,4)\) all lie in a plane \(\Pi\). --- 5 WORK AREA LINES (style=lined) --- --- 3 WORK AREA LINES (style=lined) --- A second plane, \(\psi\), has the Cartesian equation \(2 x-2 y-z=-18\). --- 4 WORK AREA LINES (style=lined) --- A line \(L\) passes through the origin and is normal to the plane \(\psi\). The line \(L\) intersects \(\psi\) at a point \(D\). --- 2 WORK AREA LINES (style=lined) --- --- 3 WORK AREA LINES (style=lined) --- --- 5 WORK AREA LINES (style=lined) --- \(\text{Area}=\dfrac{1}{2}\ \bigg|\overrightarrow{AB} \times \overrightarrow{AC}\bigg|=\dfrac{1}{2}\ \left|\begin{array}{ccc}\underset{\sim}{i} & \underset{\sim}{j} & \underset{\sim}{k} \\ 0 & 1 & 1 \\ 2 & 1 & 2\end{array}\right|=\dfrac{1}{2}\ \bigg|\underset{\sim}{i}+2 \underset{\sim}{j}-2 \underset{\sim}{k}\bigg|=\dfrac{3}{2}\) b. \(\text {Shortest distance }=1 \text { unit }\) c. \(26^{\circ}\) d. \(\underset{\sim}{r}(t)=\underset{\sim}{n} \times t=2 t \underset{\sim}{i}-2 t \underset{\sim}{j}-t \underset{\sim}{k}\) \(x=2 t, y=-2 t, z=-t \quad \text{(also accepted)}\) e. \(\text {Shortest distance }=6\) f. \(D(-4,4,2)\) \(\text{Area}=\dfrac{1}{2}\ \bigg|\overrightarrow{AB} \times \overrightarrow{AC}\bigg|=\dfrac{1}{2}\ \left|\begin{array}{ccc}\underset{\sim}{i} & \underset{\sim}{j} & \underset{\sim}{k} \\ 0 & 1 & 1 \\ 2 & 1 & 2\end{array}\right|=\dfrac{1}{2}\ \bigg|\underset{\sim}{i}+2 \underset{\sim}{j}-2 \underset{\sim}{k}\bigg|=\dfrac{3}{2}\) \(|\overrightarrow{A C}|= \displaystyle{\sqrt{2^2+1^2+2^2}}=3\) \(\dfrac{3}{2}=\dfrac{1}{2}\ |\overrightarrow{A C}| \times h \ \Rightarrow \ h=1\) \(\therefore \text { Shortest distance }=1 \text { unit }\) c. \(\text {Vector} \perp \text {to plane}\ \psi\ \text {is}\ \ \underset{\sim}{n}=2 \underset{\sim}{i}-2 \underset{\sim}{j}-\underset{\sim}{k}\) \(\text{Parallel line to}\ \underset{\sim}{r}(t) \ \text{is}\ \ \underset{\sim}{m}=\underset{\sim}{i}-2 \underset{\sim}{j}+2\underset{\sim}{k}\) \(\text{Find angle } \alpha \text{ between }\underset{\sim}{n} \text{ and } \underset{\sim}{m},\) \(\text{Solve for } \alpha:\) \((2 \underset{\sim}{i}-2 \underset{\sim}{j}-\underset{\sim}{k})(\underset{\sim}{i}-2 \underset{\sim}{j}+\underset{\sim}{2 k})=3 \times 3 \times \cos \, \alpha\) \(\Rightarrow \alpha=64^{\circ} \text { (nearest degree) }\) \(\text{Find angle } \theta \text{ between } \underset{\sim}{m} \text{ and plane } \psi :\) \(\theta=90-64=26^{\circ}\) d. \(\underset{\sim}{r}(t)=\underset{\sim}{n} \times t=2 t \underset{\sim}{i}-2 t \underset{\sim}{j}-t \underset{\sim}{k}\) \(x=2 t, y=-2 t, z=-t \quad \text{(also accepted)}\) e. \(|\overrightarrow{OD}|=\text{shortest distance from } O \text{ to plane } \psi\). \(\Rightarrow D \text{ is on } L \text{ and } \psi\) \(\text{Solve for } t: \ 2(2 t)-2(-2 t)-(t)=-18\) \(\Rightarrow t=-2\) \(|\overrightarrow{OD}|=-4 \underset{\sim}{i}+4 \underset{\sim}{j}+2 \underset{\sim}{k}\) \(\text {Shortest distance }=\displaystyle{\sqrt{(-4)^2+4^2+2^2}}=6\) f. \(\overrightarrow{OD}=-4 \underset{\sim}{i}+4 \underset{\sim}{j}+2 \underset{\sim}{i}\) \(D(-4,4,2)\)
a.
\(\overrightarrow{A B} =\overrightarrow{O B}-\overrightarrow{O A}=\left(\begin{array}{l}1 \\ 2 \\ 3\end{array}\right)-\left(\begin{array}{l}1 \\ 1 \\ 2\end{array}\right)=\left(\begin{array}{l}0 \\ 1 \\ 1\end{array}\right)\)
\(\overrightarrow{A C} =\overrightarrow{O C}-\overrightarrow{O A}=\left(\begin{array}{l}3 \\ 2 \\ 4\end{array}\right)-\left(\begin{array}{l}1 \\ 1 \\ 2\end{array}\right)=\left(\begin{array}{l}2 \\ 1 \\ 2\end{array}\right)\)
a.
\(\overrightarrow{A B} =\overrightarrow{O B}-\overrightarrow{O A}=\left(\begin{array}{l}1 \\ 2 \\ 3\end{array}\right)-\left(\begin{array}{l}1 \\ 1 \\ 2\end{array}\right)=\left(\begin{array}{l}0 \\ 1 \\ 1\end{array}\right)\)
\(\overrightarrow{A C} =\overrightarrow{O C}-\overrightarrow{O A}=\left(\begin{array}{l}3 \\ 2 \\ 4\end{array}\right)-\left(\begin{array}{l}1 \\ 1 \\ 2\end{array}\right)=\left(\begin{array}{l}2 \\ 1 \\ 2\end{array}\right)\)
b. \(\text {In } \triangle ABC \text {, shortest distance of } B \text { to } A C\ \text {is the} \perp \text {distance }\)
To calculate the mass of distant pulsars, physicists use Newton's law of universal gravitation and the equations of circular motion.
The planet Phobetor orbits pulsar PSR B1257+12 at an orbital radius of 6.9 × 10\(^{10}\) m and with a period of 8.47 × 10\(^6\) s.
Assuming that Phobetor follows a circular orbit, calculate the mass of the pulsar. Show all your working. (3 marks)
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\(M=2.71\ \times 10^{30}\ \text{kg}\)
| \(\dfrac{r^3}{T^2}\) | \(=\dfrac{GM}{4\pi^2}\) | |
| \(M\) | \(=\dfrac{4\pi^2 r^3}{G T^2}\) | |
| \(=\dfrac{4 \pi^2 \times (6.9 \times 10^{10})^3}{6.67 \times 10^{-11} \times (8.47 \times 10^6)^2}\) | ||
| \(=2.71 \times 10^{30}\ \text{kg}\) |
A schematic side view of one design of an audio loudspeaker is shown in Diagram 1 below. It uses a current carrying coil that interacts with permanent magnets to create sound by moving a cone in and out. Diagram 2 shows a schematic view of the loudspeaker from the position of the eye shown in Diagram 1. The direction of the current is clockwise, as shown. --- 0 WORK AREA LINES (style=lined) --- --- 1 WORK AREA LINES (style=lined) --- --- 6 WORK AREA LINES (style=lined) --- a. b. \(E\) c. \(2.51\ \text{N}\) a. Magnetic fields run from the north pole to the south pole. b. Apply the right-hand rule: \(\Rightarrow E\) c. \(l= 2\pi \times 5 \times 10^{-2} = 0.1\pi\) \(\therefore F=nlIB=20 \times 0.1\pi \times 2 \times 0.2=2.51\ \text{N}\)
A.
left
B.
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up the page
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down the page
E.
into the page
F.
out of the page
A forest ranger wishes to investigate the mass of adult male koalas in a Victorian forest. A random sample of 20 such koalas has a sample mean of 11.39 kg. It is known that the mass of adult male koalas in the forest is normally distributed with a standard deviation of 1 kg. --- 3 WORK AREA LINES (style=lined) --- --- 2 WORK AREA LINES (style=lined) --- The ranger wants to decrease the width of the 95% confidence interval by 60% to get a better estimate of the population mean. --- 2 WORK AREA LINES (style=lined) --- It is thought that the mean mass of adult male koalas in the forest is 12 kg. The ranger thinks that the true mean mass is less than this and decides to apply a one-tailed statistical test. A random sample of 40 adult male koalas is taken and the sample mean is found to be 11.6 kg. --- 2 WORK AREA LINES (style=lined) --- The ranger decides to apply the one-tailed test at the 1% level of significance and assumes the mass of adult male koalas in the forest is normally distributed with a mean of 12 kg and a standard deviation of 1 kg. --- 2 WORK AREA LINES (style=lined) --- --- 2 WORK AREA LINES (style=lined) --- --- 2 WORK AREA LINES (style=lined) --- Suppose that the true mean mass of adult male koalas in the forest is 11.4 kg, and the standard deviation is 1 kg. The level of significance of the test is still 1%. --- 2 WORK AREA LINES (style=lined) --- a. \((10.95,11.83)\) b. \(57\) c. \(n=125\) d. \(H_0: \mu=12, \quad H_1: \mu<12\) e.i. \(p=0.0057\) e.ii. \(\text{Since } p<0.01 \text { : reject } H_0 \text {, favour } H_1\) f. \(\text {Critical sample mean } \bar{x} \approx 11.632\) g. \(\text{Pr}(\bar{x} \geqslant 11.63217 \mid \mu=11.4) \approx 0.071\) a. \(\sigma_{\text{pop}}=1\) \(\text{Sample:}\ \ n=20,\ \ \bar{x}=11.39,\ \ \sigma_{\text {sample }}=\dfrac{1}{\sqrt{20}}\) \(\text{Find 95% C.I. (by CAS):}\) \((10.95,11.83)\) b. \(\text{95% C.I. for 60 samples calculated}\) \(\text{Number expected }(\mu \text{ within C.I.)}=0.95 \times 60=57\) c. \(\text {C.I.}=\left(11.39-1.96 \times \dfrac{1}{\sqrt{20}}, 11.39+1.96 \times \dfrac{1}{\sqrt{20}}\right)\) \(\Rightarrow \text { Interval }=2 \times 1.96 \times \dfrac{1}{\sqrt{20}}\) \(\text{Interval reduced by } 60\%\) \(\Rightarrow \text{ New interval }=0.40 \times 2 \times 1.96 \times \dfrac{1}{\sqrt{20}}\) \(\text{Solve for } n\) : \(2 \times 1.96 \times \dfrac{1}{\sqrt{n}}=0.40 \times 2 \times 1.96 \times \dfrac{1}{\sqrt{20}}\) \(\Rightarrow n=125\) d. \(H_0: \mu=12,\ \ H_1: \mu<12\) e.i. \(E(\bar{X})=\mu=12\) \(\bar{x}=11.6, \ \sigma(\bar{X})=\dfrac{1}{\sqrt{40}}\) \(p=\operatorname{Pr}(\bar{X} \leqslant 11.6)=0.0057\) e.ii. \(\text{Since}\ \ p<0.01 \text {: reject } H_0 \text {, favour } H_1\) f. \(\text{Pr}(\bar{X} \leqslant a \mid \mu=12) \geqslant 0.01\) \(\text{Find } a \text{ (by CAS):}\) \(\text{inv Norm}\left(0.01,12, \dfrac{1}{\sqrt{40}}\right) \ \Rightarrow \ a \geqslant 11.63217\) \(\text {Critical sample mean}\ \ \bar{x} \approx 11.632\) g. \(\mu=11.4,\ \ \sigma_{\text{pop}}=1,\ \ n=40\) \(\text{Pr}(\bar{X} \geqslant 11.63217 \mid \mu=11.4) \approx 0.071\)
Explain the trend in reactivity with water of the elements in Group 2 as you move down the group. (2 marks)
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The diagram shows some of the energy levels of excited neon atoms. These energy levels are not drawn to scale. --- 4 WORK AREA LINES (style=lined) --- --- 0 WORK AREA LINES (style=blank) ---
Sam undertakes a photoelectric effect experiment using the apparatus shown in Figure 1. She uses a green filter.
Sam produces a graph of photocurrent, \(I\), in milliamperes, versus voltage, \(V\), in volts, as shown in Figure 2.
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a. Stopping voltage
b. Diagram will exhibit the following points:
c. Diagram will exhibit the following points:
The following diagram represents an observation wheel, with its centre at point \(P\). Passengers are seated in pods, which are carried around as the wheel turns. The wheel moves anticlockwise with constant speed and completes one full rotation every 30 minutes.When a pod is at the lowest point of the wheel (point \(A\)), it is 15 metres above the ground. The wheel has a radius of 60 metres.
Consider the function \(h(t)=-60\ \cos(bt)+c\) for some \(b, c \in R\), which models the height above the ground of a pod originally situated at point \(A\), after time \(t\) minutes.
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After 15 minutes, the wheel stops moving and remains stationary for 5 minutes. After this, it continues moving at double its previous speed for another 7.5 minutes.
The height above the ground of a pod that was initially at point \(A\), after \(t\) minutes, can be modelled by the piecewise function \(w\):
\(w(t) = \begin {cases}
h(t) &\ \ 0 \leq t < 15 \\
k &\ \ 15 \leq t < 20 \\
h(mt+n) &\ \ 20\leq t\leq 27.5
\end{cases}\)
where \(k\geq 0, m\geq 0\) and \(n \in R\).
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iii. Sketch the graph of the piecewise function \(w\) on the axes below, showing the coordinates of the endpoints. (3 marks)
| a. | \(\text{Period:}\) | \(\dfrac{2\pi}{b}\) | \(=30\) |
| \(\therefore\ b\) | \(=\dfrac{\pi}{15}\) |
\(\text{Given }h(t)=-60\cos(bt)+c,\ \text{evaluate when }t=0, h=15\ \text{to find }c.\)
| \(-60\ \cos(0)+c\) | \(=15\) |
| \(c\) | \(=75\) |
\(\therefore\ h(t)=-60\cos(\dfrac{\pi t}{15})+75\)
| b. | \(\text{Average height}\) | \(=\dfrac{1}{\frac{30}{4}-0}\displaystyle\int_0^{\frac{30}{4}}\Bigg(-60\cos\Bigg(\dfrac{\pi}{15}t\Bigg)+75\Bigg)\,dt\) |
| \(=\dfrac{2}{15}\left[75t-\dfrac{900\ \sin(\frac{\pi}{15}t)}{\pi}\right]_{0}^{7.5}\) | ||
| \(=\dfrac{2}{15}\Bigg[75\times 7.5-\dfrac{900\ \sin(\frac{\pi}{15}\times 7.5)}{\pi}\Bigg]-\Bigg[0\Bigg]\) | ||
| \(=\dfrac{75\pi-120}{\pi}=\dfrac{15(5\pi-8)}{\pi}\) | ||
| \(=36.802\dots\approx 36.80\ \text{m}\) |
c. \(\text{Av rate of change of height}\)
| \(=\dfrac{h(7.5)-h(0)}{7.5}\) | |
| \(=\dfrac{\Bigg(75-60\cos(\dfrac{\pi \times 7.5}{15})\Bigg)-\Bigg(75-60\cos(\dfrac{\pi\times 0}{15})\Bigg)}{7.5}\) | |
| \(=\dfrac{75-15}{7.5}=8\) |
| di. | \(\text{Period is 30 minutes, so after 15 minutes pod}\) \(\text{is at the top of the wheel.}\) |
| \(\therefore\ k=75-60\ \cos(\frac{\pi}{15}\times 15)=135\) |
\(\text{Pod is travelling at twice its previous speed}\)
\(\text{so one revolution takes 15 minutes}\)
| \(\therefore\ \text{Period}\rightarrow\) | \(\dfrac{2\pi}{bm}\) | \(=15\) |
| \(bm\) | \(=\dfrac{2\pi}{15}\) | |
| \(\dfrac{\pi}{15}\cdot m\) | \(=\dfrac{2\pi}{15}\) | |
| \(m\) | \(=\dfrac{2\pi}{15}\times \dfrac{15}{\pi}\) | |
| \(=2\) |
| dii. | \(\text{When }t=20\ \text{the pod is at the top of the wheel and height is 135.}\) \(\text{When }t=27.5\ \text{the pod is back at the start and height is 15.}\) |
\(\text{Using CAS solve for }t=20:\rightarrow\ h(2(20)+n)=135\ \rightarrow\ n=30p+5\)
\(\text{Using CAS solve for }t=27.5:\rightarrow\ h(2(27.5)+n)=15\ \rightarrow\ n=30p+5\)
\(\therefore\ n=30p+5,\ p\in Z\)
Let \(f:R \rightarrow R, f(x)=x(x-2)(x+1)\). Part of the graph of \(f\) is shown below.
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a. \((-1, 0), (0, 0), (2, 0)\)
b. \(\Bigg(\dfrac{1-\sqrt{7}}{3}, \dfrac{2(7\sqrt{7}-10}{27}\Bigg), \Bigg(\dfrac{1+\sqrt{7}}{3}, \dfrac{-2(7\sqrt{7}-10}{27}\Bigg)\)
c.i. \(x=2,\ \text{or}\ x=\dfrac{-1\pm \sqrt{5}}{2}\)
c.ii. \(\text{Let }a=\dfrac{-1-\sqrt{5}}{2}\ \text{and }b=\dfrac{-1+\sqrt{5}}{2}\)
\(\text{Then}\ A=\displaystyle\int_a^b (x-2)(x^2+x-1)\,dx+\displaystyle\int_b^2 -(x-2)(x^2+x-1)\,dx\)
c.iii. \(5.95\)
d. \(\text{1st case }\rightarrow \ a=\dfrac{2\sqrt{7}+1}{3}, b=\dfrac{1-\sqrt{7}}{3}\)
\(\text{2nd case }\rightarrow \ a=\dfrac{-2\sqrt{7}+1}{3}, b=\dfrac{1+\sqrt{7}}{3}\)
a. \((-1, 0), (0, 0), (2, 0)\)
b. \(\text{Using CAS solve for}\ x:\)
\(\dfrac{d}{dx}(x(x-2)(x+1))=0\)
\(\therefore\ x=\dfrac{1-\sqrt{7}}{3}\ \text{and }x=\dfrac{1+\sqrt{7}}{3}\)
\(\text{Substitute }x\ \text{values into }f(x)\ \text{using CAS to get}\ y\ \text{values}\)
\(\text{The stationary points of }f\ \text{are}:\)
\(\Bigg(\dfrac{1-\sqrt{7}}{3}, \dfrac{2(7\sqrt{7}-10}{27}\Bigg), \Bigg(\dfrac{1+\sqrt{7}}{3}, \dfrac{-2(7\sqrt{7}-10}{27}\Bigg)\)
ci \(\text{Given }f(x)=g(x)\)
| \(x(x-2)(x+1)\) | \(=x-2\) |
| \(x(x-2)(x+1)(x-2)\) | \(=0\) |
| \((x-2)(x(x+1)-1)\) | \(=0\) |
| \((x-2)(x^2+x-1)\) | \(=0\) |
\(\therefore\ \text{Using CAS: } \)
\(x=2,\ \text{or}\ x=\dfrac{-1\pm \sqrt{5}}{2}\)
cii \(\text{Area of bounded region:}\)
\(\text{Let }a=\dfrac{-1-\sqrt{5}}{2}\ \text{and }b=\dfrac{-1+\sqrt{5}}{2}\)
\(\text{Then}\ A=\displaystyle\int_a^b (x-2)(x^2+x-1)\,dx+\displaystyle\int_b^2 -(x-2)(x^2+x-1)\,dx\)
| ciii | \(\text{Solve the integral in c.ii above using CAS:}\) |
| \(\text{Total area}=5.946045..\approx 5.95\) |
d. \(\text{Method 1 – Equating coefficients}\)
\((x-a)(x-b)^2=x(x-2)(x+1)+k\)
\(x^3-2bx^2-ax^2+b^2x+2abx-ab^2=x^3-x^2-2x+k\)
\((x^3-(a+2b)x^2+(2ab+b^2)x-ab^2=x^3-x^2-2x+k\)
\(\therefore\ -(a+2b)=-1\ \to\ a=1-2b …(1)\)
\(2ab+b^2=-2\ \ …(2)\)
\(\text{Substitute (1) into (2) and solve for }b.\)
| \(2b(1-2b)+b^2\) | \(=-2\) |
| \(3b^2-2b-2\) | \(=0\) |
| \(b\) | \(=\dfrac{1\pm \sqrt{7}}{3}\) |
| \(\text{When }b\) | \(=\dfrac{1+\sqrt{7}}{3}\) |
| \(a\) | \(=1-2\Bigg(\dfrac{1+\sqrt{7}}{3}\Bigg)=\dfrac{-2\sqrt{7}+1}{3}\) |
| \(\text{When }b\) | \(=\dfrac{1-\sqrt{7}}{3}\) |
| \(a\) | \(=1-2\Bigg(\dfrac{1-\sqrt{7}}{3}\Bigg)=\dfrac{2\sqrt{7}+1}{3}\) |
\(\text{Method 2 – Using transformations}\)
\(\text{The squared factor in }(x-a)(x-b)^2=x(x-2)(x+1)+k,\)
\(\text{shows that the turning point is on the }x\ \text{axis}.\)
\(\therefore\ \text{Lowering }f(x)\ \text{by }\dfrac{2(7\sqrt{7}-10)}{27}\ \text{and raising }f(x)\ \text{by }\dfrac{2(7\sqrt{7}+10)}{27}\)
\(\text{will give the 2 possible sets of values for }a\ \text{and}\ b.\)
\(\text{1st case – lowering using CAS solve }h(x) =0\ \rightarrow\ h(x)=f(x)-\dfrac{2(7\sqrt{7}-10)}{27}\)
\(\therefore\ x-\text{intercepts}\rightarrow \ a=\dfrac{2\sqrt{7}+1}{3}, b=\dfrac{1-\sqrt{7}}{3}\)
\(\text{2nd case – raising using CAS solve }h(x) =0\ \rightarrow\ h(x)=f(x)+\dfrac{2(7\sqrt{7}+10)}{27}\)
\(\therefore\ x-\text{intercepts}\rightarrow \ a=\dfrac{-2\sqrt{7}+1}{3}, b=\dfrac{1+\sqrt{7}}{3}\)
Which one of the following is closest to the de Broglie wavelength of a 663 kg motor car moving at 10 m s\(^{-1}\) ?
\(A\)
\(\lambda=\dfrac{h}{mv}=\dfrac{6.626 \times 10^{-34}}{663 \times 10}=9.99 \times 10^{-38} \approx 10^{-37}\ \text{m}\)
\(\Rightarrow A\)
Lucy is running horizontally at a speed of 6 m s\(^{-1}\) along a diving platform that is 8.0 m vertically above the water.
Lucy runs off the end of the diving platform and reaches the water below after time \(t\).
She lands feet first at a horizontal distance \(d\) from the end of the diving platform.
Question 9
Which one of the following expressions correctly gives the distance \(d\) ?
Question 10
Which one of the following is closest to the time taken, \(t\), for Lucy to reach the water below?
\(\text{Question 9:} \ B\)
\(\text{Question 10:} \ C\)
Question 9
\(\Rightarrow B\)
Question 10
Find time of flight \((t):\)
| \(s\) | \(=ut+\dfrac{1}{2}at^2\) | |
| \(s\) | \(=\dfrac{1}{2}at^2\ \ \ (u=0)\) | |
| \(t\) | \(=\sqrt{\dfrac{2s}{a}}=\sqrt{\dfrac{2 \times 8}{9.8}}\approx 1.3\ \text{s}\) |
\(\Rightarrow C\)
A mobile phone charger uses a step-down transformer to transform 240 V AC mains voltage to 5.0 V. The mobile phone draws a current of 3.0 A while charging. Assume that the transformer is ideal and that all readings are RMS.
Calculate the current drawn from the mains during charging? (2 marks)
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\(0.06\ \text{A}\)
| \(\text{Power}_{\text{in}}\) | \(=\ \text{Power}_{\text{out}}\) | |
| \(V_p I_p\) | \(=V_s I_s\) | |
| \(I_p\) | \(=\dfrac{V_s I_s}{V_p}=\dfrac{5 \times 3}{240}=0.06\ \text{A}\) |
A magnet approaches a coil with six turns, as shown in the diagram below. During time interval \(\Delta t\), the magnetic flux changes by 0.05 Wb and the average induced EMF is 1.2 V.
Which one of the following is closest to the time interval \(\Delta t\) ?
\(C\)
| \(\varepsilon\) | \(=N\dfrac{\Delta \Phi}{\Delta t}\) | |
| \(\Delta t\) | \(=N \dfrac{\Delta \Phi}{\varepsilon}=6 \times \dfrac{0.05}{1.2}=0.25\ \text{s}\) |
\(\Rightarrow C\)
A materials scientist is studying the diffraction of electrons through a thin metal foil. She uses electrons with an energy of 10.0 keV. The resulting diffraction pattern is shown in Figure 19. --- 6 WORK AREA LINES (style=lined) --- The materials scientist then increases the energy of the electrons by a small amount and hence their speed by a small amount. Explain what effect this would have on the de Broglie wavelength of the electrons. Justify your answer. (3 marks) --- 6 WORK AREA LINES (style=lined) --- a. \(0.012\ \text{nm}\) b. Effects when speed of the electron increases by a small amount: a. Convert electron volts to joules: \(\Rightarrow \ E=10 \times 10^3 \times 1.602 \times 10^{-19}=1.602 \times 10^{-15}\ \text{J}\)
b. Effects when speed of the electron increases by a small amount:
\(E\)
\(=\dfrac{1}{2}mv^2\)
\(v\)
\(=\sqrt{\dfrac{2E}{m}}\)
\(=\sqrt{\dfrac{2 \times 1.602 \times 10^{-15}}{9.109 \times 10^{-31}}}\)
\(=5.93 \times 10^7\)
\(\therefore \lambda\)
\(=\dfrac{h}{mv}\)
\(=\dfrac{6.626 \times 10^{-34}}{9.109 \times 10^{-27} \times 5.93 \times 10^7}\)
\(=1.23 \times 10^{-11}\ \text{m}\)
\(=0.012\ \text{nm}\)
The graph of \(y=x+\dfrac{1}{x}\) is shown over part of its domain.
Use two trapeziums of equal width to approximate the area between the curve, the \(x\)-axis and the lines \(x=1\) and \(x=3\). (2 marks)
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\(5\dfrac{1}{6}\)
\(\text{Trapezium rule approximation (see formula sheet):}\)
\begin{array} {|c|c|}
\hline
\rule{0pt}{2.5ex} x\rule[-1ex]{0pt}{0pt} & 1&2&3 \\
\hline
\rule{0pt}{2.5ex} f(x)\rule[-1ex]{0pt}{0pt} & 1+1=2 & 2+\dfrac{1}{2}=\dfrac{5}{2} & 3+ \dfrac{1}{3}=\dfrac{10}{3}\\
\hline
\end{array}
| \(\text{Area}\) | \(\approx \dfrac{3-1}{2\times 2}\Bigg[2+2\times\dfrac{5}{2}+\dfrac{10}{3}\Bigg]\) |
| \(\approx\dfrac{1}{2}\Bigg[\dfrac{6}{3}+\dfrac{15}{3}+\dfrac{10}{3}\Bigg]\) | |
| \(\approx5\dfrac{1}{6}\) |
Let \(y=\dfrac{x^2-x}{e^x}\).
Find and simplify \(\dfrac{dy}{dx}\). (2 marks)
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\(\dfrac{-x^2+3x-1}{e^x}\)
\(\text{Using the quotient rule:}\)
| \(\dfrac{dy}{dx}\) | \(=\dfrac{e^x(2x-1)-(x^2-x)e^x}{(e^x)^2}\) |
| \(=\dfrac{e^x(-x^2+3x-1)}{e^{2x}}\) | |
| \(=\dfrac{-x^2+3x-1}{e^x}\) |
Solve \(e^{2x}-12=4e^{x}\) for \(x\ \in\ R\). (3 marks)
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\(x=\log_{e}6\)
| \(e^{2x}-12\) | \(=4e^{x}\) |
| \(e^{2x}-4e^{x}-12\) | \(=0\) |
\(\text{Let}\ \ u=e^{x}:\)
| \(u^2-4u-12\) | \(=0\) |
| \((u-6)(u+2)\) | \(=0\) |
\(\Rightarrow u=6\ \ \ \text{or}\ -2\)
| \(\therefore e^{x}\) | \(=6\ \ \ \ \ \ \ \ \ \ \text{or}\ \ \ \ \ \ e^{x}=-2\ \text{(no solution)}\) | |
| \(x\) | \(=\log_{e}6 \) |
The diagram shows a simple alternator consisting of a rectangular coil of area 0.060 m\(^{2}\) and 200 turns, rotating in a uniform magnetic field. The magnetic flux through the coil in the vertical position shown in the diagram is 1.2 × 10\(^{-3}\) Wb.
Calculate the strength of the magnetic field. Show your working. (2 marks)
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a. \(0.02\ \text{T}\)
b. \(2.4\ \text{V}\)
| a. | \(\Phi\) | \(=BA\) |
| \(B\) | \(=\dfrac{\Phi}{A}=\dfrac{1.2 \times 10^{-3}}{0.060}=0.02\ \text{T}\) |
b. \(\text{The time for 1 complete rotation:}\)
\(T=\dfrac{1}{f}=\dfrac{1}{2.5}=0.4\ \text{s}\)
\(\Rightarrow \text{Time for a quarter turn}\ =0.1\ \text{s}\)
\(\varepsilon=N\dfrac{\Delta \Phi}{t}=200 \times \dfrac{1.2 \times 10^{-3}}{0.1}=2.4\ \text{V}\)
A wind generator provides power to a factory located 2.00 km away, as shown in the diagram. When there is a moderate wind blowing steadily, the generator produces a voltage of 415 V and a current of 100 A. The total resistance of the transmission wires between the wind generator and the factory is 2.00 \(\Omega\). --- 2 WORK AREA LINES (style=lined) --- To operate correctly, the factory's machinery requires a power supply of 40 kW. --- 6 WORK AREA LINES (style=lined) --- The factory's owner decides to limit transmission energy loss by installing two transformers: a step-up transformer with a turns ratio of 1:10 at the wind generator and a step-down transformer with a turns ratio of 10:1 at the factory. Each transformer can be considered ideal. With the installation of the transformers, determine the power, in kilowatts, now supplied to the factory. (3 marks) --- 8 WORK AREA LINES (style=lined) --- a. \(41.5\ \text{kW}\) b. \(P_{\text{loss}}=I^2R=100^2 \times 2=20000\ \text{W}=20\ \text{kW}\) \(\Rightarrow\ \text{Net power supplied}\ =41.5-20=21.5\ \text{kW}\ < 40\ \text{kW}\) \(\therefore \ \text{The power supply will not be enough to power the factory.}\) c. \(41.3\ \text{kW}\) a. \(P=VI=415 \times 100 = 41\ 500\ \text{W}=41.5\ \text{kW}\) b. \(P_{\text{loss}}=I^2R=100^2 \times 2=20000\ \text{W}=20\ \text{kW}\) \(\Rightarrow\ \text{Net power supplied}\ =41.5-20=21.5\ \text{kW}\ < 40\ \text{kW}\) \(\therefore \ \text{The power supply will not be enough to power the factory.}\) \(P_{\text{loss}} \text{(new)} =I^2R=10^2 \times 2=200\ \text{W}=0.2\ \text{kW}\) \(\therefore\ \text{Net power supplied}\ =41.5-0.2=41.3\ \text{kW}\)
c.
\(\dfrac{I_s}{I_p}\)
\(=\dfrac{N_p}{N_s}\)
\(I_s\)
\(=\dfrac{N_p}{N_s} \times I_p=\dfrac{1}{10} \times 100=10\ \text{A}\)
A schematic diagram of a mass spectrometer that is used to deflect charged particles to determine their mass is shown in the diagram. Positive singly charged ions (with a charge of +1.602 × 10\(^{-19}\) C) are produced at the ion source. These are accelerated between an anode and a cathode. The potential difference between the anode and the cathode is 1500 V. The ions pass into a region of uniform magnetic field, \(B\), and are directed by the field into a semicircular path of diameter \(D\).
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Each ion has a mass of 4.80 × 10\(^{-27}\) kg.
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a. \(2.403 \times 10^{-16}\ \text{J}\)
| b. | \(\Delta KE\) | \(=\dfrac{1}{2}mv^2\) |
| \(v\) | \(=\sqrt{\dfrac{2 \Delta KE}{m}}\) | |
| \(=\sqrt{\dfrac{2 \times 2.403 \times 10^{-16}}{4.80 \times 10^{-27}}}\) | ||
| \(=3.16 \times 10^5\ \text{ms}^{-1}\) |
c. \(0.19\ \text{m}\)
| b. | \(\Delta KE\) | \(=\dfrac{1}{2}mv^2\) |
| \(v\) | \(=\sqrt{\dfrac{2 \Delta KE}{m}}\) | |
| \(=\sqrt{\dfrac{2 \times 2.403 \times 10^{-16}}{4.80 \times 10^{-27}}}\) | ||
| \(=3.16 \times 10^5\ \text{ms}^{-1}\) |
| c. | \(F_B\) | \(=F_c\) |
| \(qvB\) | \(=\dfrac{mv^2}{r}\) | |
| \(r\) | \(=\dfrac{mv}{qB}\) | |
| \(=\dfrac{4.80 \times 10^{-27} \times 3.16 \times 10^5}{1.602 \times 10^{-19} \times 0.10}\) | ||
| \(=0.095\ \text{m}\) |
\(\therefore\ D=0.19\ \text{m}\)
There are over 400 geostationary satellites above Earth in circular orbits. The period of orbit is one day (86 400 seconds). Each geostationary satellite remains stationary in relation to a fixed point on the equator. The diagram shows an example of a geostationary satellite that is in orbit relative to a fixed point, \(\text{X}\), on the equator. --- 4 WORK AREA LINES (style=lined) --- --- 8 WORK AREA LINES (style=lined) --- --- 7 WORK AREA LINES (style=lined) --- a. Reasons the satellite must orbit relative to a fixed point on the equator: b. See worked solutions c. 3076 ms\(^{-1}\) a. Reasons the satellite must orbit relative to a fixed point on the equator:
b.
\(\dfrac{r^3}{T^2}\)
\(=\dfrac{GM}{4\pi^2}\)
\(r\)
\(=\sqrt[3]{\dfrac{GMT^2}{4\pi^2}}\)
\(=\sqrt[3]{\dfrac{6.67 \times 10^{-11} \times 5.98 \times 10^{24} \times (86\ 400)^2}{4\pi^2}}\)
\(=42.250 \times 10^6\ \text{m}\)
\(\therefore \ \text{Altitude}\ =42.250 \times 10^6 -6.37 \times 10^6 =3.59 \times 10^7\ \text{m}\)
c.
\(v\)
\(=\sqrt{\dfrac{GM}{r}}\)
\(=\sqrt{\dfrac{6.67 \times 10^{-11} \times 5.98 \times 10^{24}}{42.25 \times 10^6}}\)
\(=3073\ \text{ms}^{-1}\)
The diagram shows four positions (1, 2, 3 and 4) of the coil of a single-turn, simple DC motor. The coil is turning in a uniform magnetic field that is parallel to the plane of the coil when the coil is in Position 1, as shown. When the motor is operating, the coil rotates about the axis through the middle of sides \(L M\) and \(N K\) in the direction indicated. The coil is attached to a commutator. Current for the motor is passed to the commutator by brushes that are not shown in the diagram. --- 3 WORK AREA LINES (style=lined) --- When the coil is in Position 3, in which direction is the current flowing in the side \(KL-\) from \(K\) to \(L\) or --- 2 WORK AREA LINES (style=lined) --- The side \(K L\) of the coil has a length of 0.10 m and experiences a magnetic force of 0.15 N due to the magnetic field, which has a magnitude of 0.5 T. Calculate the magnitude of the current in the coil. (2 marks) --- 5 WORK AREA LINES (style=lined) --- a. \(K\) to \(L\) b. \(L\) to \(K\) c. \(3\ \text{A}\) a. Using the right hand rule: b. Using the right hand rule:
from \(L\) to \(K\)? (1 marks)
c.
\(F\)
\(=lIB\)
\(I\)
\(=\dfrac{F}{lB}=\dfrac{0.15}{0.1 \times 0.5}=3\ \text{A}\)
Gamma radiation is often used to treat cancerous tumours. The energy of a gamma photon emitted by radioactive cobalt-60 is 1.33 MeV.
Which one of the following is closest to the frequency of the gamma radiation?
\(B\)
\(\Rightarrow B\)
Which one of the following best provides evidence of electrons behaving as waves?
\(D\)
\(\Rightarrow D\)
A simple electricity generator is shown in the diagram below. When the coil is rotated, the output voltage across the slip rings is measured. The graph shows how the output voltage varies with time.
The frequency of rotation of the generator is now doubled.
Which one of the following graphs best represents the output voltage measured across the slip rings?
\(C\)
\(\Rightarrow C\)
Fluorescent lights, when operating, contain gaseous mercury atoms, as shown in Figure 1. Analysis of the light produced by fluorescent lights shows a number of emission spectral lines, including a prominent line representing a wavelength of 436.6 nm. --- 4 WORK AREA LINES (style=lined) --- --- 0 WORK AREA LINES (style=lined) --- a. \(E=2.84\ \text{eV}\) b. a. \(E=\dfrac{hc}{\lambda}=\dfrac{6.626 \times 10^{-34} \times 3 \times 10^8}{436.6 \times 10^{-9}}=4.549 \times 10^{-19}\ \text{J}\) \(\text{Convert to eV:}\) \(E= \dfrac{4.549 \times 10^{-19}}{1.602 \times 10^{-19}} = 2.84\ \text{eV}\) b.
A fish farmer releases 200 fish into a pond that originally contained no fish. The fish population, \(P\), grows according to the logistic model, \(\dfrac{d P}{d t}=P\left(1-\dfrac{P}{1000}\right)\) , where \(t\) is the time in years after the release of the 200 fish. --- 2 WORK AREA LINES (style=lined) --- One form of the solution for \(P\) is \(P=\dfrac{1000}{1+D e^{-t}}\ \), where \(D\) is a real constant. --- 2 WORK AREA LINES (style=lined) --- The farmer releases a batch of \(n\) fish into a second pond, pond 2 , which originally contained no fish. The population, \(Q\), of fish in pond 2 can be modelled by \(Q=\dfrac{1000}{1+9 e^{-1.1 t}}\), where \(t\) is the time in years after the \(n\) fish are released. --- 2 WORK AREA LINES (style=lined) --- --- 2 WORK AREA LINES (style=lined) --- --- 4 WORK AREA LINES (style=lined) --- --- 4 WORK AREA LINES (style=lined) --- --- 0 WORK AREA LINES (style=lined) --- The farmer wishes to take 5.5% of the fish from pond 2 each year. The modified logistic differential equation that would model the fish population, \(Q\), in pond 2 after \(t\) years in this situation is \(\dfrac{d Q}{d t}=\dfrac{11}{10}\, Q\left(1-\dfrac{Q}{1000}\right)-0.055Q\) --- 4 WORK AREA LINES (style=lined) --- a. \(A=1, \quad B=\dfrac{1}{1000}\) b. \(\Rightarrow D=4\) c. \(n=\dfrac{1000}{1+9 e^0}=100\) d. \(Q=\dfrac{1000}{1+9 e^{-6.6}} \approx 988\) e.i. \(Q^{\prime}=\frac{121}{100}\, Q\left(1-\frac{Q}{1000}\right)^2-\frac{121}{100\ 000}\left(1-\frac{Q}{1000}\right)\) e.ii. \(t=2\) f. g. \(Q=950\) a. \(\dfrac{dP}{dt}=P\left(1-\dfrac{P}{1000}\right) \ \Rightarrow \ \dfrac{d t}{d P}=\dfrac{1}{P}\left(\dfrac{1}{1-\frac{P}{1000}}\right)\) \(\text{Expand (by CAS):}\) \(\dfrac{1}{P}\left(\dfrac{1}{1-\frac{P}{1000}}\right)=\dfrac{1}{P}-\dfrac{1}{(P-1000)}=\dfrac{1}{P}+\dfrac{1}{1000}\left(\dfrac{1}{1-\frac{P}{1000}}\right)\) \(A=1, \quad B=\dfrac{1}{1000}\) b. \(\text{When}\ \ t=0, P=200 \text{ (given)}\) \(\text{Solve}\ \ 200=\dfrac{1000}{1+D e^0}\ \ \text{for}\ t:\) \(\Rightarrow D=4\ \ \text {(by CAS):}\) c. \(Q=\dfrac{1000}{1+9 e^{-1.1 t}}\) \(\text{At}\ \ t=0, Q=n\): \(n=\dfrac{1000}{1+9 e^0}=100\) d. \(\text{Find } Q \text{ when } t=6:\) \(Q=\dfrac{1000}{1+9 e^{-6.6}} \approx 988\) e.i. \(\dfrac{d Q}{d t}=\dfrac{11}{10}\, Q\left(1-\dfrac{Q}{1000}\right)\) \(\text{Using the product rule:}\) \begin{aligned} e.ii. \(\text{Max } Q^{\prime} \Rightarrow Q^{\prime \prime}=0\) \(\text{Solve } Q^{\prime \prime}=0 \ \ \text {(by CAS):}\) \(\Rightarrow Q=500\) \(\text{Solve } Q=500 \text{ for } t \text{ (by CAS):}\) \(t=1.99 \ldots=2 \ \text{(nearest year)}\) f. g. \(\text{Solve for } Q \ \text{(by CAS):}\) \(\dfrac{d Q}{d t}=\dfrac{11}{10}\, Q\left(1-\dfrac{Q}{1000}\right)-0.055\,Q=0\) \(\Rightarrow Q=950\)
Q^{\prime \prime} & =\frac{11}{10}\left[Q^{\prime}\left(1-\frac{Q}{1000}\right)+Q\left(-\frac{1}{1000}\, Q^{\prime}\right)\right] \\
& =\frac{11}{10}\left[\frac{11}{10}\, Q\left(1-\frac{Q}{1000}\right)^2-\frac{Q}{1000}\left(\frac{11}{10}\, Q\left(1-\frac{Q}{1000}\right)\right)\right] \\
& =\frac{121}{100}\, Q\left(1-\frac{Q}{1000}\right)^2-\frac{121}{100\ 000}\left(1-\frac{Q}{1000}\right)
\end{aligned}
A group of physics students undertake a Young's double-slit experiment using the apparatus shown in the diagram. They use a green laser that produces light with a wavelength of 510 nm. The light is incident on two narrow slits, S\(_1\) and S\(_2\). The distance between the two slits is 100 \( \mu \)m.
An interference pattern is observed on a screen with points P\(_{0}\), P\(_{1}\) and P\(_2\) being the locations of adjacent bright bands, as shown. Point P\(_0\) is the central bright band.
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a. \(1.02 \times 10^{-6}\ \text{m}\)
b. The spacing between adjacent bright bands will increase.
c. Evidence for the wave-like nature of light:
a. \(\text{Difference in distance}\ = 2 \lambda\)
\(\text{Path difference}\ =2 \times 510 \times 10^{-9} = 1.02 \times 10^{-6}\ \text{m}\).
b. The spacing will increase.
c. Evidence for the wave-like nature of light:
A proton in an accelerator beamline of proper length 4.80 km has a Lorentz factor, \(\gamma\), of 2.00.
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a. \(0.866c\)
b. \(2.4\ \text{km}\)
| a. \(\dfrac{1}{\sqrt{1-\frac{v^2}{c^2}}}\) | \(=2\) | |
| \(\sqrt{1-\dfrac{v^2}{c^2}}\) | \(=\dfrac{1}{2}\) | |
| \(1-\dfrac{v^2}{c^2}\) | \(=\dfrac{1}{4}\) | |
| \(\dfrac{v^2}{c^2}\) | \(=\dfrac{3}{4}\) | |
| \(v^2\) | \(=\dfrac{3}{4}c^2\) | |
| \(v\) | \(=0.866c\) |
| b. | \(l\) | \(=l_0\sqrt{1-\dfrac{v^2}{c^2}}\) |
| \(=4.8 \times \sqrt{1-\dfrac{(0.886c)^2}{c^2}}\) | ||
| \(=4.8 \times 0.5\) | ||
| \(=2.4\ \text{km}\) |
Giorgos is practising his tennis serve using a tennis ball of mass 56 g. --- 5 WORK AREA LINES (style=lined) --- --- 5 WORK AREA LINES (style=lined) --- --- 7 WORK AREA LINES (style=lined) --- a. \(1.2\ \text{s}\) b. \(4.7\ \text{ms}^{-1}\) c. \(1.475\ \text{m}\) a. Time to for the ball to fall from max height back to shoulder level: \(\text{Total time of flight}\ =0.606 \times 2=1.2\ \text{s}\) b. The racket travels a quarter of the circumference of the circle in 0.606 seconds. \(v=\dfrac{d}{t}=\dfrac{2\pi \times 1.8 \times 0.25}{0.606}=4.7\ \text{ms}^{-1}\) c. Time for the ball to reach the net: \(t=\dfrac{d}{v}=\dfrac{12}{24}=0.5\ \text{s}\) Vertical displacement from max height in 0.5 seconds: \(s=ut+\dfrac{1}{2}at^2=0 \times 0.5 + \dfrac{1}{2} \times 9.8 \times 0.5^2=1.225\ \text{m}\). \(\text{Height (at net)}\ =3.6-1.225=2.375\ \text{m}\). \(\therefore\ \text{Height (above net)}\ =2.375-0.9=1.475\ \text{m}\)
\(s\)
\(=ut+\dfrac{1}{2}at^2\)
\(1.8\)
\(=0 \times t + \dfrac{1}{2} \times 9.8 \times t^2\)
\(t\)
\(=\sqrt{\dfrac{1.8}{4.9}}=0.606\ \text{s}\)
The curve given by \(y^2=x-1\), where \(2 \leq x \leq 5\), is rotated about the \(x\)-axis to form a solid of revolution. --- 2 WORK AREA LINES (style=lined) --- --- 2 WORK AREA LINES (style=lined) --- --- 4 WORK AREA LINES (style=lined) --- --- 2 WORK AREA LINES (style=lined) --- The total surface area of the solid consists of the curved surface area plus the areas of the two circular discs at each end. The 'efficiency ratio' of a body is defined as its total surface area divided by the enclosed volume. --- 2 WORK AREA LINES (style=lined) --- --- 4 WORK AREA LINES (style=lined) --- a.i. \(\displaystyle V=\pi \int y^2 d x=\pi \int_2^5(x-1) dx\) a.ii. \(\text{Evaluating integral (by calc):}\) \(V=\dfrac{15 \pi}{2}\ \text{u}^3\) b.i. \(\displaystyle y=\sqrt{x-1} \ \Rightarrow \ \frac{d y}{d x}=\frac{1}{2} \cdot \frac{1}{\sqrt{x-1}} \ \Rightarrow \ \frac{d^2 y}{dx^2}=\frac{1}{4(x-1)}\) \(\ \ \begin{aligned} \displaystyle \int_2^5 2 \pi \sqrt{x-1} \ \sqrt{1+\frac{1}{4(x-1)}} \ d x & =\int_2^5 2 \pi \sqrt{x-1+\frac{1}{4}}\, d x \\ & =\pi \int_2^5 \sqrt{4 x-3}\, d x\end{aligned}\) \(\text {S.A.}=30.847\ \text{u}^2\) c. \(y=\sqrt{x-1}\) \(\text{At}\ \ x=2\ \ \Rightarrow y=1\) \(\text{At}\ \ x=5\ \ \Rightarrow y=2\) \begin{aligned} \(\text {Efficiency ratio}=\dfrac{46.5545}{\frac{15 \pi}{2}}=1.98\ \text{(2 d.p.)}\) d. \(V=\displaystyle \pi \int_2^k(x-1) d x=24 \pi\) \(\text{Solve (by calc):}\) \(\dfrac{\pi k(k-2)}{2}=24 \pi \ \Rightarrow \ k=8 \) \(\text {S.A.}=\pi \displaystyle{\int_2^8} \sqrt{4 x-3}\, d x=75.9163 \ldots\) \(\text{Total S.A.}=75.9163+\pi(1+7)=101.049 \) \(\text{Efficiency ratio}=\dfrac{101.049}{24 \pi}= 1.34\ \text{(2 d.p.)}\) a.i. \(\displaystyle V=\pi \int y^2 d x=\pi \int_2^5(x-1) dx\) a.ii. \(\text{Evaluating integral (by calc):}\) \(V=\dfrac{15 \pi}{2}\ \text{u}^3\) b.i. \(\displaystyle y=\sqrt{x-1} \ \Rightarrow \ \frac{d y}{d x}=\frac{1}{2} \cdot \frac{1}{\sqrt{x-1}} \ \Rightarrow \ \frac{d^2 y}{dx^2}=\frac{1}{4(x-1)}\) \(\ \ \begin{aligned} \displaystyle \int_2^5 2 \pi \sqrt{x-1} \ \sqrt{1+\frac{1}{4(x-1)}} \ d x & =\int_2^5 2 \pi \sqrt{x-1+\frac{1}{4}}\, d x \\ & =\pi \int_2^5 \sqrt{4 x-3}\, d x\end{aligned}\) \(\text {S.A.}=30.847\ \text{u}^2\) c. \(y=\sqrt{x-1}\) \(\text{At}\ \ x=2\ \ \Rightarrow y=1\) \(\text{At}\ \ x=5\ \ \Rightarrow y=2\) \begin{aligned} \(\text {Efficiency ratio}=\dfrac{46.5545}{\frac{15 \pi}{2}}=1.98\ \text{(2 d.p.)}\) d. \(V=\displaystyle \pi \int_2^k(x-1) d x=24 \pi\) \(\text{Solve (by calc):}\) \(\dfrac{\pi k(k-2)}{2}=24 \pi \ \Rightarrow \ k=8 \) \(\text {S.A.}=\pi \displaystyle{\int_2^8} \sqrt{4 x-3}\, d x=75.9163 \ldots\) \(\text{Total S.A.}=75.9163+\pi(1+7)=101.049 \) \(\text{Efficiency ratio}=\dfrac{101.049}{24 \pi}= 1.34\ \text{(2 d.p.)}\)
b.ii. \(\text{Evaluate integral in b.i.}\)
\text{Total S.A. } &=30.847+\pi(1)^2+\pi(2)^2 \\
&=46.5545\ \text{u}^2 \\
\end{aligned}
b.ii. \(\text{Evaluate integral in b.i.}\)
\text{Total S.A. } &=30.847+\pi(1)^2+\pi(2)^2 \\
&=46.5545\ \text{u}^2 \\
\end{aligned}
Let \(w=\text{cis}\left(\dfrac{2 \pi}{7}\right)\). --- 2 WORK AREA LINES (style=lined) --- --- 2 WORK AREA LINES (style=lined) --- --- 0 WORK AREA LINES (style=blank) --- --- 0 WORK AREA LINES (style=lined) --- --- 3 WORK AREA LINES (style=lined) --- --- 4 WORK AREA LINES (style=lined) --- --- 3 WORK AREA LINES (style=lined) --- use De Moivre's theorem to show that --- 8 WORK AREA LINES (style=lined) --- a. \(w^7-1 =\ \text{cis} \Big{(}\dfrac{2 \pi}{7} \Big{)}^7-1 = \text{cis} \Big{(}\dfrac{14 \pi}{7}\Big{)}-1 = 1-1=0\) \(\therefore w\ \text{is a root of}\ \ z^7-1=0 \) b. \(\text{Roots of}\ \ z^7-1=0:\) \(\text{cis} (0), \text{cis} \Big{(}\dfrac{2 \pi}{7} \Big{)}, \text{cis} \Big{(}\dfrac{4 \pi}{7} \Big{)}, \text{cis} \Big{(}\dfrac{6 \pi}{7} \Big{)}, \text{cis} \Big{(}\dfrac{8 \pi}{7} \Big{)}, \text{cis} \Big{(}\dfrac{10 \pi}{7} \Big{)}, \text{cis} \Big{(}\dfrac{12 \pi}{7} \Big{)} \) c. d.i. d.ii. \(\text{Base angle (isosceles Δ)}\ = \dfrac{1}{2} \times \Big{(}\pi-\dfrac{2\pi}{7}\Big{)} = \dfrac{5\pi}{14} \) \(\arg(z-1)=\dfrac{9\pi}{14} \) f.i. \(\text{cis}\Big{(}\dfrac{2\pi}{7}\Big{)} + \text{cis}\Big{(}\dfrac{12\pi}{7}\Big{)} = \text{cis}\Big{(}\dfrac{2\pi}{7}\Big{)} + \text{cis}\Big{(}-\dfrac{2\pi}{7}\Big{)} =2\cos\Big{(}\dfrac{2\pi}{7}\Big{)} \) f.ii. \(z^6+z^5+z^4+z^3+z^2+z+1=0\ \ \text{(using part (e))} \) \((z^6+z)+(z^4+z^3)+(z^5+z^2)=-1 \) \(\Bigg{(}\text{cis}\Big{(}\dfrac{12\pi}{7}\Big{)} + \text{cis}\Big{(}\dfrac{2\pi}{7}\Big{)}\Bigg{)} + \Bigg{(}\text{cis}\Big{(}\dfrac{8\pi}{7}\Big{)} + \text{cis}\Big{(}\dfrac{6\pi}{7}\Big{)}\Bigg{)} + \Bigg{(}\text{cis}\Big{(}\dfrac{10\pi}{7}\Big{)} + \text{cis}\Big{(}\dfrac{4\pi}{7}\Big{)}\Bigg{)}=-1\) \(2\cos \Big{(}\dfrac{2 \pi}{7}\Big{)}+2\cos \Big{(}\dfrac{6 \pi}{7}\Big{)}+2\cos \Big{(}\dfrac{4 \pi}{7}\Big{)}=-1\) \(\cos \Big{(}\dfrac{2 \pi}{7}\Big{)}+\cos \Big{(}\dfrac{4 \pi}{7}\Big{)}+\cos \Big{(}\dfrac{6 \pi}{7}\Big{)}=-\dfrac{1}{2}\) a. \(w^7-1 =\ \text{cis} \Big{(}\dfrac{2 \pi}{7} \Big{)}^7-1 = \text{cis} \Big{(}\dfrac{14 \pi}{7}\Big{)}-1 = 1-1=0\) \(\therefore w\ \text{is a root of}\ \ z^7-1=0 \) b. \(\text{Roots of}\ \ z^7-1=0:\) \(\text{cis} (0), \text{cis} \Big{(}\dfrac{2 \pi}{7} \Big{)}, \text{cis} \Big{(}\dfrac{4 \pi}{7} \Big{)}, \text{cis} \Big{(}\dfrac{6 \pi}{7} \Big{)}, \text{cis} \Big{(}\dfrac{8 \pi}{7} \Big{)}, \text{cis} \Big{(}\dfrac{10 \pi}{7} \Big{)}, \text{cis} \Big{(}\dfrac{12 \pi}{7} \Big{)} \) c. d.i. d.ii. \(\text{Base angle (isosceles Δ)}\ = \dfrac{1}{2} \times \Big{(}\pi-\dfrac{2\pi}{7}\Big{)} = \dfrac{5\pi}{14} \) \(\arg(z-1)=\dfrac{9\pi}{14} \) f.i. \(\text{cis}\Big{(}\dfrac{2\pi}{7}\Big{)} + \text{cis}\Big{(}\dfrac{12\pi}{7}\Big{)} = \text{cis}\Big{(}\dfrac{2\pi}{7}\Big{)} + \text{cis}\Big{(}-\dfrac{2\pi}{7}\Big{)} =2\cos\Big{(}\dfrac{2\pi}{7}\Big{)} \) f.ii. \(z^6+z^5+z^4+z^3+z^2+z+1=0\ \ \text{(using part (e))} \) \((z^6+z)+(z^4+z^3)+(z^5+z^2)=-1 \) \(\Bigg{(}\text{cis}\Big{(}\dfrac{12\pi}{7}\Big{)} + \text{cis}\Big{(}\dfrac{2\pi}{7}\Big{)}\Bigg{)} + \Bigg{(}\text{cis}\Big{(}\dfrac{8\pi}{7}\Big{)} + \text{cis}\Big{(}\dfrac{6\pi}{7}\Big{)}\Bigg{)} + \Bigg{(}\text{cis}\Big{(}\dfrac{10\pi}{7}\Big{)} + \text{cis}\Big{(}\dfrac{4\pi}{7}\Big{)}\Bigg{)}=-1\) \(2\cos \Big{(}\dfrac{2 \pi}{7}\Big{)}+2\cos \Big{(}\dfrac{6 \pi}{7}\Big{)}+2\cos \Big{(}\dfrac{4 \pi}{7}\Big{)}=-1\) \(\cos \Big{(}\dfrac{2 \pi}{7}\Big{)}+\cos \Big{(}\dfrac{4 \pi}{7}\Big{)}+\cos \Big{(}\dfrac{6 \pi}{7}\Big{)}=-\dfrac{1}{2}\)
e.
\((z-1)(z^6+z^5+z^4+z^3+z^2+z+1) \)
\(=(z^7+z^6+z^5+z^4+z^3+z^2+z)-(z^6+z^5+z^4+z^3+z^2+z+1) \)
\(=z^7-1\)
e.
\((z-1)(z^6+z^5+z^4+z^3+z^2+z+1) \)
\(=(z^7+z^6+z^5+z^4+z^3+z^2+z)-(z^6+z^5+z^4+z^3+z^2+z+1) \)
\(=z^7-1\)
Let \(f(x)=e^{x-1}\).
Given that the product function \(f(x)\times g(x)=e^{(x-1)^2}\), the rule for the function \(g\) is
\(B\)
| \(f(x)\times g(x)\) | \(=e^{(x-1)^2}\) |
| \(e^{x-1}\times g(x)\) | \(=e^{(x-1)^2}\) |
| \( g(x)\) | \(=\dfrac{e^{(x-1)^2}}{e^{(x-1)}}\) |
| \(=e^{(x-1)^2}\times e^{(x-1)^-1}\) | |
| \(=e^{x^2-3x+2}\) | |
| \(=e^{(x-2)(x-1)}\) |
\(\Rightarrow B\)
A manufacturer produces tennis balls.
The diameter of the tennis balls is a normally distributed random variable \(D\), which has a mean of 6.7 cm and a standard deviation of 0.1 cm.
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Tennis balls are packed and sold in cylindrical containers. A tennis ball can fit through the opening at the top of the container if its diameter is smaller than 6.95 cm.
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A tennis ball is classed as grade A if its diameter is between 6.54 cm and 6.86 cm, otherwise it is classed as grade B.
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A tennis coach uses both grade A and grade B balls. The serving speed, in metres per second, of a grade A ball is a continuous random variable, \(V\), with the probability density function
\(f(v) = \begin {cases}
\dfrac{1}{6\pi}\sin\Bigg(\sqrt{\dfrac{v-30}{3}}\Bigg) &\ \ 30 \leq v \leq 3\pi^2+30 \\
0 &\ \ \text{elsewhere}
\end{cases}\)
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The serving speed of a grade B ball is given by a continuous random variable, \(W\), with the probability density function \(g(w)\).
A transformation maps the graph of \(f\) to the graph of \(g\), where \(g(w)=af\Bigg(\dfrac{w}{b}\Bigg)\).
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a. \(0.1587\)
b. \(d\approx6.83\)
c. \(0.9938\)
d. \(0.9998\)
e. \(0,8960\)
f. \(0.06\)
g. \(90\%\)
h. \(0.1345\)
i. \(3(\pi^2+4)\)
j. \(a=\dfrac{3}{2}, b=\dfrac{2}{3}\)
a. \(\text{Normal distribution:}\to \mu=6.7, \sigma=0.1\)
\(D\sim N(6.7, 0.1^2)\)
\(\text{Using CAS: }[\text{normCdf}(6.8, \infty, 6.7, 0.1)]\)
\(\Pr(D>6.8)=0.15865…\approx0.1587\)
b. \(\Pr(D<d)=0.90\)
\(\Pr\Bigg(Z<\dfrac{d-6.7}{0.1}\Bigg)=0.90\)
\(\text{Using CAS: }[\text{invNorm}(0.9, 6.7, 0.1)]\)
\(\therefore\ d=6.828155…\approx6.83\ \text{cm}\)
c. \(\text{Normal distribution:}\to \mu=6.7, \sigma=0.1\)
\(D\sim N(6.7, 0.1^2)\)
\(\text{Using CAS: }[\text{normCdf}(-\infty, 6.95, 6.7, 0.1)]\)
\(\Pr(D<6.95)=0.99379…\approx0.9938\)
d. \(\text{Binomial:}\to n=4, p=0.99379…\)
\(X=\text{number of balls}\)
\(X\sim \text{Bi}(4, 0.999379 …)\)
\(\text{Using CAS: }[\text{binomCdf}(4, 0.999379 …, 3, 4)]\)
\(\Pr(X\geq 3)=0.99977 …\approx 0.9998\)
| e. | \(\Pr(\text{Grade A|Fits})\) | \(=\Pr(6.54<D<6.86|D<6.95)\) |
| \(=\dfrac{\Pr(6.54<D<6.86)}{\Pr(D<6.95)}\) | ||
| \(\text{Using CAS: }\) | \(=\Bigg[\dfrac{\text{normCdf}(6.54, 6.86, 6.7, 0.1)}{\text{normCdf}(-\infty, 6.95, 6.7, 0.1)}\Bigg]\) | |
| \(=\dfrac{0.89040…}{0.99977…}\) | ||
| \(=0.895965…\approx 0.8960\) |
f. \(\text{Normally distributed → symmetrical}\)
\(\text{Pr ball diameter outside the 99% interval}=1-0.99=0.01\)
\(D\sim N(6.7, \mu^2)\)
\(\Pr(6.54<D<6.86)>0.99\)
\(\therefore\ \Pr(D<6.54)<\dfrac{1-0.99}{2}\)
\(\text{Find z score using CAS: }\Bigg[\text{invNorm}\Bigg(\dfrac{1-0.99}{2},0,1\Bigg)\Bigg]=-2.575829…\)
\(\text{Then solve:} \ \dfrac{6.54-6.7}{\sigma}<-2.575829…\)
\(\therefore\ \sigma<0.0621\approx 0.06\)
g. \(\hat{p}=\dfrac{0.7382+0.9493}{2}=0.84375\)
\(\text{Solve the following simultaneous equations for }z, \hat{p}=0.84375\)
| \(0.84375-z\sqrt{\dfrac{0.84375(1-0.84375)}{32}}\) | \(=0.7382\) | \((1)\) |
| \(0.84375+z\sqrt{\dfrac{0.84375(1-0.84375)}{32}}\) | \(=0.9493\) | \((2)\) |
| \(\text{Equation}(2)-(1)\) | ||
| \(2z\sqrt{\dfrac{0.84375(1-0.84375)}{32}}\) | \(=0.2111\) | |
| \(z=\dfrac{0.10555}{\sqrt{\dfrac{0.84375(1-0.84375)}{32}}}\) | \(=1.64443352\) |
\(\text{Alternatively using CAS: Solve the following simultaneous equations for }z, \hat{p}\)
| \(\hat{p}-z\sqrt{\dfrac{\hat{p}(1-\hat{p})}{32}}\) | \(=0.7382\) |
| \(\text{and}\) | |
| \(\hat{p}+z\sqrt{\dfrac{\hat{p}(1-\hat{p})}{32}}\) | \(=0.9493\) |
\(\rightarrow \ z=1.64444…\ \text{and}\ \hat{p}=0.84375\)
\(\therefore\ \text{Using CAS: normCdf}(-1.64443352, 1.64443352, 0 , 1)\)
\(\text{Level of Confidence} =0.89999133…=90\%\)
h. \(\text{Using CAS: Evaluate }\to \displaystyle \int_{50}^{3\pi^2+30} \frac{1}{6\pi}\sin\Bigg(\sqrt{\dfrac{v-30}{3}}\Bigg)\,dx=0.1345163712\approx 0.1345\)
i. \(\text{Using CAS: Evaluate }\to \displaystyle \int_{30}^{3\pi^2+30} v.\dfrac{1}{6\pi}\sin\Bigg(\sqrt{\dfrac{v-30}{3}}\Bigg)\,dx=3(\pi^2+4)=3\pi^2+12\)
j. \(\text{When the function is dilated in both directions, }a\times b=1\)
\(\text{Method 1 : Simultaneous equations}\)
\(g(w) = \begin {cases}
\dfrac{b}{6\pi}\sin\Bigg(\sqrt{\dfrac{\dfrac{w}{b}-30}{3}}\Bigg) &\ \ 30b \leq v \leq b(3\pi^2+30) \\
\\ 0 &\ \ \text{elsewhere}
\end{cases}\)
\(\text{Using CAS: Define }g(w)\ \text{and solve the simultaneous equations below for }a, b.\)
\(\displaystyle \int_{30.b}^{b.(3\pi^2+30)} g(w)\,dw=1\)
\(\displaystyle \int_{30.b}^{b.(3\pi^2+30)} w.g(w)\,dw=2\pi^2+8\)
\(\therefore\ b=\dfrac{2}{3}\ \text{and}\ a=\dfrac{3}{2}\)
\(\text{Method 2 : Transform the mean}\)
| \(\text{Area}\) | \(=1\) |
| \(\therefore\ a\) | \(=\dfrac{1}{b}\) |
| \(\to\ b\) | \(=\dfrac{E(W)}{E(V)}\) |
| \(=\dfrac{2\pi^2+8}{3\pi^2+12}\) | |
| \(=\dfrac{2(\pi^2+4)}{3(\pi^2+4)}\) | |
| \(=\dfrac{2}{3}\) |
|
| \(\therefore\ a\) | \(=\dfrac{3}{2}\) |
Viewed from above, a scenic walking track from point \(O\) to point \(D\) is shown below. Its shape is given by \(f(x)= \begin{cases}-x(x+a)^2, & 0 \leq x \leq 1 \\ e^{x-1}-x+b, & 1<x \leq 2 .\end{cases}\) The minimum turning point of section \(O A B C\) occurs at point \(A\). Point \(B\) is a point of inflection and the curves meet at point \(C(1,0)\). Distances are measured in kilometres. --- 3 WORK AREA LINES (style=lined) --- --- 5 WORK AREA LINES (style=lined) --- --- 3 WORK AREA LINES (style=lined) --- --- 3 WORK AREA LINES (style=lined) --- The return track from point \(D\) to point \(O\) follows an elliptical path given by \(x=2 \cos (t)+2, y=(e-2) \sin (t)\), where \(t \in\left[\dfrac{\pi}{2}, \pi\right]\). --- 3 WORK AREA LINES (style=lined) --- --- 0 WORK AREA LINES (style=lined) --- --- 2 WORK AREA LINES (style=lined) --- --- 2 WORK AREA LINES (style=lined) --- a. \(\text{At}\ C(1,0): \) \(\underset{x \to 1^{-}}{\lim} f_1(x) = \underset{x \to 1^{-}}{\lim}-x(x+a)^2 = -1(1+a)^2 = 0 \) \(a=-1\) \(\underset{x \to 1^{+}}{\lim} f_2(x)\ \underset{x \to 1^{+}}{\lim} (e^{x-1}-x+b) = e^0-1+b=b = 0 \) b. \(\text{Find derivative functions (by calc)}:\) \(\dfrac{d}{dx} \big{(}-x(x-1)^2\big{)} = -(x-1)(3x-1)\ \ \Rightarrow \ \ \text{At}\ \ x=1, f_1^{′}(x)=0 \) \(\dfrac{d}{dx} (e^{x-1}-x+b) = e^{x-1}-1\ \ \Rightarrow \ \ \text{At}\ \ x=1, f_2^{′}(x)=0 \) \(\Rightarrow\ \text{Since gradients are equal, curves meet smoothly.}\) c.i. \(A\Big{(} \frac{1}{3}, -\frac{4}{27} \Big{)} \) c.ii. \(B\Big{(} \frac{2}{3}, -\frac{2}{27} \Big{)} \) d. \(\Big{(}\dfrac{x-2}{2}\Big{)}^2 + \Big{(}\dfrac{y}{e-2}\Big{)}^2=1\) e. f.i. \(\displaystyle{\int_{\frac{\pi}{2}}^{\pi}} \sqrt{4\,\sin^2(t)+(e-2)^2\cos^2(t)}\,dt\) f.ii. \(\text{Length}\ = 2.255\) a. \(\text{At}\ C(1,0): \) \(\underset{x \to 1^{-}}{\lim} f_1(x) = \underset{x \to 1^{-}}{\lim}-x(x+a)^2 = -1(1+a)^2 = 0 \) \(a=-1\) \(\underset{x \to 1^{+}}{\lim} f_2(x)\ \underset{x \to 1^{+}}{\lim} (e^{x-1}-x+b) = e^0-1+b=b = 0 \) b. \(\text{Find derivative functions (by calc)}:\) \(\dfrac{d}{dx} \big{(}-x(x-1)^2\big{)} = -(x-1)(3x-1)\ \ \Rightarrow \ \ \text{At}\ \ x=1, f_1^{′}(x)=0 \) \(\dfrac{d}{dx} (e^{x-1}-x+b) = e^{x-1}-1\ \ \Rightarrow \ \ \text{At}\ \ x=1, f_2^{′}(x)=0 \) \(\Rightarrow\ \text{Since gradients are equal, curves meet smoothly.}\) c.i. \(\dfrac{d}{dx} \big{(}-x(x-1)^2\big{)} = -(x-1)(3x-1)\ \Rightarrow \ \text{SP when}\ x=\dfrac{1}{3} \) \(A\Big{(} \frac{1}{3}, -\frac{4}{27} \Big{)} \) c.ii. \(\text{POI at}\ B: \ f_1^{″}(x)=-6x+4=0\ \ \Rightarrow x=\dfrac{2}{3} \) \(B\Big{(} \frac{2}{3}, -\frac{2}{27} \Big{)} \) d. \(\dfrac{x-2}{2}=\cos(t), \ \ \dfrac{y}{e-2}=\sin(t) \) \(\Big{(}\dfrac{x-2}{2}\Big{)}^2 + \Big{(}\dfrac{y}{e-2}\Big{)}^2=1\) e. f.i. \(\dfrac{dx}{dt} = -2\sin(t),\ \ \dfrac{dy}{dt} = (e-2)\cos(t) \) \(\displaystyle{\int_{\frac{\pi}{2}}^{\pi}} \sqrt{4\,\sin^2(t)+(e-2)^2\cos^2(t)}\,dt\) f.ii. \(\text{Evaluate the integral in part f.i.}\) \(\Rightarrow \text{Length}\ = 2.255\)
Two high-voltage transmission lines span a distance of 260 km between Power Plant A and Town B, as shown in the diagram. Power Plant A provides 350 MW of power. The potential difference at Power Plant A is 500 kV. The current in the transmission lines has a value of 700 A and the power loss in the transmission lines is 20 MW.
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a. \(41\ \Omega\)
b. The power generated in the power plant is 500 kV.
\(V_{\text{drop}}=IR=700 \times 41 =28.7\ \text{kV} \)
\(V_{\text{remaining}} = 500-28.7 = 471.3\ \text{kV} \)
\(\therefore\) 480V will not be available to Town B.
c. If the voltage was decreased by a factor of 10 to 50 kV:
| a. | \(P_{\text{loss}}\) | \(=I^2R\) |
| \(R\) | \(=\dfrac{P_{\text{loss}}}{I^2}=\dfrac{20 \times 10^6}{700^2}=41\ \Omega\) |
b. The power generated in the power plant is 500 kV.
\(V_{\text{drop}}=IR=700 \times 41 =28.7\ \text{kV} \)
\(V_{\text{remaining}} = 500-28.7 = 471.3\ \text{kV} \)
\(\therefore\) 480V will not be available to Town B.
c. If the voltage was decreased by a factor of 10 to 50 kV:
Figure 1 shows a single square loop of conducting wire placed just outside a constant uniform magnetic field, \(B\). The length of each side of the loop is 0.040 m. The magnetic field has a magnitude of 0.30 T and is directed out of the page.
Over a time period of 0.50 s, the loop is moved at a constant speed, \(v\), from completely outside the magnetic field, Figure 1, to completely inside the magnetic field, Figure 2.
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a. \(9.6 \times 10^{-4}\ \text{V}\)
b.
| a. | \(\varepsilon\) | \(=\dfrac{\Delta \phi}{\Delta t}\) |
| \(=\dfrac{\Delta B A}{\Delta t}\) | ||
| \(=\dfrac{0.3 \times 0.04^2}{0.5}\) | ||
| \(=9.6 \times 10^{-4}\ \text{V}\) |
b.
Let \(f:R \to R, f(x)=e^x+e^{-x}\) and \(g:R \to R, g(x)=\dfrac{1}{2}f(2-x)\).
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Two functions \(g_1\) and \(g_2\) are created, both with the same rule as \(g\) but with distinct domains, such that \(g_1\) is strictly increasing and \(g_2\) is strictly decreasing.
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Shown below is the graph of \(g\), the inverse of \(g_1\) and \(g_2\), and the line \(y=x\).
The intersection points between the graphs of \(y=x, y=g(x)\) and the inverses of \(g_1\) and \(g_2\), are labelled \(P\) and \(Q\).
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Let \(h:R\to R, h(x)=\dfrac{1}{k}f(k-x)\), where \(k\in (o, \infty)\).
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Let \(h_1:[k, \infty)\to R, h_1(x)=h(x)\).
The rule for the inverse of \(h_1\) is \(y=\log_{e}\Bigg(\dfrac{1}{k}x+\dfrac{1}{2}\sqrt{k^2x^2-4}\Bigg)+k\)
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It is possible for the graphs of \(h\) and the inverse of \(h_1\) to intersect twice. This occurs when \(k=5\).
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a. \(\text{Reflect in the }y\text{-axis}\)
\(\text{Then translate 2 units to the right}\)
\(\text{OR}\)
\(\text{Translate 2 units to the left}\)
\(\text{Then reflect in the }y\text{-axis}\)
\(\text{OR}\)
\(\text{Translate 2 units to the right only }(f \ \text{even function})\)
b. \(\text{See worked solution}\)
c.i. \(P(1.27, 1.27\), Q(4.09, 4.09)\)
c.ii. \(2\displaystyle \int_{1.27…}^{4.09…} (x-g(x))\,dx=5.56\)
d. \(n=-1\)
e. \(k\approx 1.27\)
f. \(A=43.91\)
a. \(\text{Reflect in the }y\text{-axis}\)
\(\text{Then translate 2 units to the right}\)
\(\text{OR}\)
\(\text{Translate 2 units to the left}\)
\(\text{Then reflect in the }y\text{-axis}\)
\(\text{OR}\)
\(\text{Translate 2 units to the right only }(f \ \text{even function})\)
b. \(\text{Some options include:}\)
• \(\text{Domain}\to [1, \infty)\ \ \ \text{Range}\to [2, \infty)\)
\(\text{or}\)
• \(\text{Domain}\to (1, \infty)\ \ \ \text{Range}\to (2, \infty)\)
\(\text{If functions split at turning point } (2, 1)\ \text{then possible options:}\)
• \(\text{Domain}\ g_1\to [2, \infty)\ \ \ \text{Range}\to [1, \infty)\)
\(\text{and }\)
\(\text{Domain}\ g_1^{-1}\to [1, \infty)\ \ \ \text{Range}\to [2, \infty)\)
\(\text{or}\)
• \(\text{Domain}\ g_1\to (2, \infty)\ \ \ \text{Range}\to (1, \infty)\)
\(\text{and }\)
\(\text{Domain}\ g_1^{-1}\to (1, \infty)\ \ \ \text{Range}\to (2, \infty)\)
c.i. \(\text{By CAS:}\ P(1.27, 1.27), Q(4.09, 4.09)\)
| c.ii. | \(\text{Area}\) | \(=2\displaystyle \int_{1.27…}^{4.09…} (x-g(x))\,dx\) |
| \(=2\displaystyle \int_{1.27…}^{4.09…} \Bigg(x-\dfrac{1}{2}\Big(e^{2-x}+e^{x-2}\Big)\Bigg)\,dx\) | ||
| \(\approx 5.56\) |
d. \((0, 2)\ \text{turning pt of }f(x)\)
\(\text{and }h(x) \text{is the transformation from }f(x)\)
\(\therefore \Bigg(k, \dfrac{2}{k}\Bigg)\ \text{turning tp of }h(x)\)
\(\text{so the coordinates have the relationship}\)
\(y=\dfrac{2}{x}=2x^{-1}\)
\(\therefore\ n=-1\)
e. \(\text{Smallest }k\ \text{is when inverse of the curves }h_1\ \text{and}\ h\)
\(\text{touch with the line }y=x.\)
| \(\therefore\ h(x)\) | \(=\dfrac{1}{k}\Big(e^{k-x}+e^{x-k}\Big)\) |
| \(=x\) |
| \(\text{and}\ h'(x)\) | \(=\dfrac{1}{k}\Big(-e^{k-x}+e^{x-k}\Big)\) |
| \(=1\) |
\(\text{at point of intersection, where }k>0.\)
\(\text{Using CAS graph both functions to solve or solve as simultaneous equations.}\)
\(\rightarrow\ k\approx 1.2687\approx 1.27\)
f. \(\text{When}\ k=5\)
\(h_1^{-1}(x)=\log_e\Bigg(\dfrac{5}{2}x+\dfrac{1}{2}\sqrt{25x^2-4}\Bigg)+5\)
\(\text{and }h(x)=\dfrac{1}{5}\Big(e^{5-x}+e^{x-5}\Big)\)
\(\text{Using CAS: values of }x\ \text{at of intersection of fns are}\)
\(x\approx 1.45091…\ \text{and}\ 8.78157…\)
| \(\text{Area}\) | \(=\displaystyle \int_{1.45091…}^{8.78157…}h_1^{-1}(x)- h(x)\,dx\) |
| \(=\displaystyle \int_{1.45091…}^{8.78157…} \log_e\Bigg(\dfrac{5}{2}x+\dfrac{1}{2}\sqrt{25x^2-4}\Bigg)+5-\dfrac{1}{5}\Big(e^{5-x}+e^{x-5}\Big)\,dx\) | |
| \(=43.91\) |
A transformer is used to provide a low-voltage supply for six outdoor garden globes. The circuit is shown in the diagram below. Assume there is no power loss in the connecting wires. The input of the transformer is connected to a power supply that provides an AC voltage of 240 V. The globes in the circuit are designed to operate with an AC voltage of 12 V. Each globe is designed to operate with a power of 20 W. --- 2 WORK AREA LINES (style=lined) --- The globes are turned on. --- 4 WORK AREA LINES (style=lined) --- --- 4 WORK AREA LINES (style=lined) --- a. \(20:1\) b. \(0.5\ \text{A}\) c. AC input current: a. \(\dfrac{N_p}{N_s}=\dfrac{240}{12}=20:1\) b. The total power drawn on the secondary side \(=6 \times 20=120\ \text{W}\) Total power on the primary side is \(120\ \text{W}\). \(I=\dfrac{P}{V}=\dfrac{120}{240}=0.5\ \text{A}\) c. AC input current:
The diagram below shows the spectrum of light emitted by a hydrogen vapour lamp. The spectral line indicated by the arrow on the diagram is in the visible region of the spectrum.
Calculate the frequency of the light corresponding to the spectral line indicated by the arrow. (2 marks)
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\(B\)
\(\lambda = 655\ \text{nm}\ = 655 \times 10^{-9}\ \text{m}\)
\(f=\dfrac{c}{\lambda}=\dfrac{3 \times 10^8}{655 \times 10^{-9}} \approx 4.6 \times 10^{14}\ \text{Hz}\)
Which one of the following statements best describes the type of light produced from different types of light sources?
\(A\)
\(\Rightarrow A\)
Which one of the following statements best explains why it is possible to compare X-ray and electron diffraction patterns?
\(B\)
\(\Rightarrow B\)
Phobos is a small moon in a circular orbit around Mars at an altitude of 6000 km above the surface of Mars. The gravitational field strength of Mars at its surface is 3.72 N kg\(^{-1}\). The radius of Mars is 3390 km. --- 6 WORK AREA LINES (style=lined) --- --- 7 WORK AREA LINES (style=lined) --- --- 5 WORK AREA LINES (style=lined) --- a. \(0.48\ \text{N kg}^{-1}\) b. \(2.77 \times 10^4\ \text{s}\) c. The orbital period will become shorter. a. \(\text{Find the mass of Mars:}\)
c. \(T=\sqrt{\dfrac{4\pi^2 r^3}{GM}}\) \(T \propto \sqrt{r^3}\) \(\therefore\) Decreasing the orbital radius will also decrease the orbital period.
\(g\)
\(=\dfrac{GM}{r^2}\)
\(M\)
\(=\dfrac{gr^2}{G}\)
\(=\dfrac{3.72 \times (3390 \times 10^3)^2}{6.67 \times 10^{-11}}\)
\(=6.409 \times 10^{23}\)
\(\text{Find the gravitational field strength where}\ \ r= 9390\ \text{km:}\)
\(g\)
\(=\dfrac{GM}{r^2}\)
\(=\dfrac{6.67 \times 10^{-11} \times 6.41 \times 10^{23}}{(9\ 390\ 000)^2}\)
\(=0.48\ \text{N kg}^{-1}\)
b.
\(\dfrac{r^3}{T^2}\)
\(=\dfrac{GM}{4\pi^2}\)
\(T\)
\(=\sqrt{\dfrac{4\pi^2 r^3}{GM}}\)
\(=\sqrt{\dfrac{4\pi^2 (9\ 390\ 000)^3}{6.67 \times 10^{-11} \times 6.409 \times 10^{23}}}\)
\(=27\ 652\ \text{s}\)
\(=2.77 \times 10^4\ \text{s}\)
COMMENT: Rounded calculations, such as using 6.41 × 10^23 were marked as wrong.
An engineer is designing a banked circular curve of radius 25 m in a new bicycle velodrome.
Diagram A shows the bicycle approaching the banked section, and diagram B shows the front view of a bicycle moving out of the page as it rounds the banked bend.
The bicycle is travelling at 11 m s\(^{-1}\) on the banked section. At this speed there are no sideways frictional forces between the wheels and the road surface.
Determine the angle of the banked bend with the road surface, giving your answer to the nearest degree. (3 marks)
\(26^{\circ}\)
| \(\tan \theta\) | \(=\dfrac{F_c}{mg}\) | |
| \(F_c\) | \(=mg \tan \theta\) | |
| \(\dfrac{mv^2}{r}\) | \(=mg \tan \theta\) | |
| \(\dfrac{v^2}{r}\) | \(=g \tan \theta\) | |
| \(\tan \theta\) | \(=\dfrac{v^2}{gr}=\dfrac{11^2}{9.8 \times 25}\) | |
| \(\theta\) | \(=\tan^{-1}\Big(\dfrac{11^2}{9.8 \times 25}\Big)=26^{\circ}\) |
The diagram below shows a stationary circular coil of conducting wire connected to a low-resistance globe in a uniform, constant magnetic field, \(B\).
Question 5
The magnetic field is switched off.
Which one of the following best describes the globe in the circuit \( \textbf{before} \) the magnetic field is switched off, \( \textbf{during} \) the time the magnetic field is being switched off and \( \textbf{after} \) the magnetic field is switched off?
\begin{align*}
\begin{array}{l}
\rule{0pt}{2.5ex} \ \rule[-1ex]{0pt}{0pt}& \\
\rule{0pt}{2.5ex}\textbf{A.}\rule[-1ex]{0pt}{0pt}\\
\rule{0pt}{2.5ex}\textbf{B.}\rule[-1ex]{0pt}{0pt}\\
\rule{0pt}{2.5ex}\textbf{C.}\rule[-1ex]{0pt}{0pt}\\
\rule{0pt}{2.5ex}\textbf{D.}\rule[-1ex]{0pt}{0pt}\\
\end{array}
\begin{array}{|c|c|}
\hline
\rule{0pt}{2.5ex}\quad\text{Before}\quad\rule[-1ex]{0pt}{0pt}&\quad \text{During} \quad& \quad\text{After}\quad\\
\hline
\rule{0pt}{2.5ex}\text{Off}\rule[-1ex]{0pt}{0pt}&\text{On}& \text{Off}\\
\hline
\rule{0pt}{2.5ex}\text{On}\rule[-1ex]{0pt}{0pt}& \text{On}& \text{Off}\\
\hline
\rule{0pt}{2.5ex}\text{On}\rule[-1ex]{0pt}{0pt}& \text{Off} & \text{Off}\\
\hline
\rule{0pt}{2.5ex}\text{Off}\rule[-1ex]{0pt}{0pt}& \text{On} & \text{On}\\
\hline
\end{array}
\end{align*}
Question 6
The radius of the coil is 5 cm and the magnetic field strength is 0.2 T. The coil has 100 loops. Assume that the magnetic field is perpendicular to the area of the coil.
Which one of the following is closest to the magnitude of the magnetic flux through the coil of wire when the magnetic field is switched on?
\(\text{Question 5:}\ A\)
\(\text{Question 6:}\ A\)
Question 5
\(\Rightarrow A\)
Question 6
\(\phi=BA=B \times \pi \times r^2 = 0.2 \times \pi \times (0.05)^2= 0.0016\ \text{Wb}\)
One type of loudspeaker consists of a current-carrying coil within a radial magnetic field, as shown in the diagram below. \(X\) and \(Y\) are magnetic poles, and the direction of the current, \(I\), in the coil is clockwise as shown.
The force, \(F\), acting on the current-carrying coil is directed into the page.
Which one of the following statements correctly identifies the magnetic polarities of \(X\) and \(Y\)?
\(A\)
\(\Rightarrow A\)
A company accountant knows that the amount owed on any individual unpaid invoice is normally distributed with a mean of $800 and a standard deviation of $200.
What is the probability, correct to three decimal places, that in a random sample of 16 unpaid invoices the total amount owed is more than $13 500?
\(B\)
\(n=16, \ E(X)=\mu=800 \)
\(X\ \sim\ N(800, 200^2) \)
\(\bar{X} \sim N\Bigg{(}800, \dfrac{200^2}{\sqrt{16}}\Bigg{)} \sim N(800, 50^2) \)
\(\text{Pr} (\Sigma X>13\ 500) = \text{Pr}\Bigg{(}\bar{X} > \dfrac{13\ 500}{16}\Bigg{)} = \text{Pr}(\bar{X} > 843.75)= 0.190…\)
\(\Rightarrow B\)
Let X be a normal random variable with mean of 100 and standard deviation of 20. Let Y be a normal random variable with mean of 80 and standard deviation of 10.
Which of the diagrams below best represents the probability density functions for X and Y, plotted on the same set of axes?
| A. |
B. | |||
| C. | D. | |||
| E. |
|
\(A\)
\(X\sim N(100, 20^2)\ \ \ Y\sim N(80, 10^2)\)
\(\text{Mean }X>\text{Mean }Y \ \text{ie peak of }X\ \text{is to the right.}\)
\(\longrightarrow\ \text{Eliminate B and E}\)
\(\text{SD }X>\text{SD }Y\ \therefore\ X\ \text{has a greater spread ie curve flatter.} \)
\(\longrightarrow\ \text{Eliminate C and D}\)
\(\Rightarrow A\)
Consider the vectors \(\underset{\sim}{\text{a}}=\alpha \underset{\sim}{\text{i}}+\underset{\sim}{\text{j}}-\underset{\sim}{\text{k}}, \ \underset{\sim}{\text{b}}=3 \underset{\sim}{\text{i}}+\beta \underset{\sim}{\text{j}}+4 \underset{\sim}{\text{k}}\) and \(\underset{\sim}{\text{c}}=2 \underset{\sim}{\text{i}}-7 \underset{\sim}{\text{j}}+\gamma \underset{\sim}{\text{k}}\), where \(\alpha, \beta, \gamma \in R\). If \(\underset{\sim}{\text{a}} \times \underset{\sim}{\text{b}}=\underset{\sim}{\text{c}}\), then
\(C\)
\begin {aligned}\underset{\sim}{\text{a}} \times \underset{\sim}{\text{b}}=\left|\begin{array}{ccc}
\underset{\sim}{\text{i}} & \underset{\sim}{\text{j}} & \underset{\sim}{\text{k}} \\ \alpha & 1 & -1 \\ 3 & \beta & 4\end{array}\right|\ & =(4+\beta)\underset{\sim}{\text{i}}-(4\alpha+3)\underset{\sim}{\text{j}}+(\alpha \beta-3) \underset{\sim}{\text{k}} \end{aligned}
\(\text{Equating coefficients given}\ \ \underset{\sim}{\text{a}} \times \underset{\sim}{\text{b}}=\underset{\sim}{\text{c}}:\)
\(4+\beta =2\ \ \Rightarrow \ \beta=-2 \)
\(4\alpha +3 = 7 \ \ \Rightarrow \ \alpha = 1 \)
\(\alpha \beta-3=\gamma \ \ \Rightarrow \ \gamma=-5 \)
\(\Rightarrow C\)
A student throws a ball for his dog to retrieve. The position vector of the ball, relative to an origin \(O\) at ground level \(t\) seconds after release, is given by \( \underset{\sim}{\text{r}}{}_\text{B} (t)=5 t \underset{\sim}{\text{i}}+7 t \underset{\sim}{\text{j}}+(15 t-4.9 t^2+1.5) \underset{\sim}{\text{k}} \). Displacement components are measured in metres, where \(\underset{\sim}{\text{i}}\) is a unit vector to the east, \(\underset{\sim}{\text{j}}\) is a unit vector to the north and \( \underset{\sim} {\text{k}}\) is a unit vector vertically up.
Calculate the total vertical distance, in metres, travelled by the ball before it hits the ground. Give your answer correct to one decimal place. (3 marks)
\(24.5\ \text{m} \)
\(\text{Upwards distance}\ (z) = 15t-4.9t^2+1.5\)
\(\dfrac{dz}{dt}=15-9.8t\)
\(\text{Find}\ t\ \text{when}\ \dfrac{dz}{dt}=0\ \text{(vertical max):} \)
\(15-9.8t=0\ \ \Rightarrow \ \ t=\dfrac{15}{9.8} \)
\(z\Big{(}t=\frac{15}{9.8}\Big{)} = 15 \times \Big{(}\dfrac{15}{9.8}\Big{)}-4.9 \times \Big{(}\dfrac{15}{9.8}\Big{)}^2 + 1.5 \approx 12.98\ \text{m} \)
\(\text{At}\ \ t=0, \ z=1.5 \)
\(\therefore \text{Total vertical distance}\ = (12.98-1.5)+12.98 = 24.5\ \text{m (1 d.p.)} \)
If the sum of two unit vectors is a unit vector, then the magnitude of the difference of the two vectors is
\(D\)
\(\text{Vectors can be drawn as two sides of an equilateral triangle.}\)
\(\text{Using the cosine rule for the difference between the two vectors:}\)
| \(c^2\) | \(=a^2+b^2-2ab\, \cos C\) | |
| \(=1+1-2\times -\dfrac{1}{2} \) | ||
| \(=3\) | ||
| \(c\) | \(=\sqrt{3}\) |
\(\Rightarrow D\)
A tourist in a hot air balloon, which is rising vertically at 2.5 m s\(^{-1}\), accidentally drops a phone over the side when the phone is 80 metres above the ground.
Assuming air resistance is negligible, how long in seconds, correct to two decimal places, does it take for the phone to hit the ground?
\(E\)
\(\text{Take upward velocity as positive.}\)
\(u=2.5\ \text{ms}^{-1}, \ a=-9.8\ \text{ms}^{-2} \)
\(\text{Using}\ \ s=ut+\dfrac{1}{2}at^2,\)
\(\text{Find}\ t\ \text{when}\ \ s=-80\ \text{(by calc):} \)
\(-80=2.5t-4.9t^2\ \ \Rightarrow \ \ t=4.30\ \text{s}\)
\(\Rightarrow E\)
The acceleration, \(a\) ms\(^{-2}\), of a particle that starts from rest and moves in a straight line is described by \(a=1+v\), where \(v\) ms\(^{-1}\) is its velocity after \(t\) seconds.
Determine the velocity of the particle after \( \log _e(e+1) \) seconds. (3 marks)
\(e\ \text{ms}^{-1}\)
\(\dfrac{dv}{dt}=1+v\ \ \Rightarrow \ \dfrac{dt}{dv} = \dfrac{1}{1+v} \)
\(t= \displaystyle{\int \dfrac{1}{1+v}\ dv} = \log_e{(1+v)}+c \)
\(\text{When}\ \ t=0, v=0\ \ \Rightarrow \ c=0 \)
| \(t\) | \(=\log_e(1+v) \) | |
| \(1+v\) | \(=e^t\) | |
| \(v\) | \(=e^t-1\) |
\(\text{At}\ \ t=\log_e(e+1): \)
\(v=e^{\log_e{(e+1)}}-1 = e+1-1=e\ \text{ms}^{-1} \)
A continuous random variable \(X\) has the following probability density function
\(g(x) = \begin {cases}
\dfrac{x-1}{20} &\ \ 1 \leq x < 6 \\
\\
\dfrac{9-x}{12} &\ \ 6 \leq x < 9 \\
\\ 0 &\ \ \ \text{elsewhere}
\end{cases}\)
The value of \(k\) such that \(\text{Pr}(X<k)=0.35\) is
\(B\)
\(\displaystyle \int_{1}^{6} \dfrac{x-1}{20}\,dx=0.625>0.35\)
\(\therefore\ k\ \text{lies between 1 and 6 so solve for interval }1\leq x\leq k\)
\(\text{Solve for}\ k\ \text{(by CAS)}:\)
\(\displaystyle \int_{1}^{k} \dfrac{x-1}{20}\,dx=0.35\ \ \Rightarrow \ \ k=\sqrt{14}+1\)
\(\Rightarrow B\)
Let \(f(x)=\log_{e}x\), where \(x>0\) and \(g(x)=\sqrt{1-x}\), where \(x<1\).
The domain of the derivative of \((f\circ g)(x)\) is
\(C\)
\(\text{Given }f(x)=\log_{e}x\ \ \text{and}\ \ g(x)=\sqrt{1-x}\)
\((f\circ g)(x)=\log_{e}\sqrt{1-x}=\dfrac{1}{2}\log_{e}(1-x)\)
\((f\circ g)^{′}(x)=\dfrac{1}{2}\times\dfrac{-1}{1-x}=\dfrac{1}{2(x-1)}\ \text{ where}\ \ x<1\)
\(\Rightarrow C\)
Which one of the following functions has a horizontal tangent at \((0, 0)\)?
\(D\)
\(\text{Index must be greater than 1 otherwise the gradient function }\)
\(\text{will not be defined at }x=0.\)
\(y=x^{\frac{4}{3}}\ \ \Rightarrow \ \dfrac{dy}{dx}=\frac{4}{3}x^{\frac{1}{3}}\ \ (\text{only option defined at}\ x=0)\)
\(\Rightarrow D\)
Consider the system of simultaneous equations below containing the parameter \(k\).
| \(kx+5y\) | \(=k+5\) |
| \(4x+(k+1)y\) | \(=0\) |
The value(s) of \(k\) for which the system of equations has infinite solutions are
\(B\)
| \(kx+5y\) | \(=k+5\) | \(\ \ \rightarrow\ \ \ \ \) | \(y\) | \(=-\dfrac{k}{5}x+\dfrac{k+5}{5}\) |
| \(4x+(k+1)y\) | \(=0\) | \(\ \ \rightarrow\ \ \ \ \) | \(y\) | \(=-\dfrac{4}{k+1}x+0\) |
\(\text{Infinite solutions when gradients and }y\text{-intercepts equal.}\)
\(\text{Equating gradients (by CAS):}\)
\(-\dfrac{k}{5}=-\dfrac{4}{k+1}\ \ \Rightarrow\ \ k=4\ \text{ or}\ -5\)
\(\text{Equating intercepts:}\)
\(\dfrac{k+5}{5}=0\ \ \Rightarrow \ \ k=-5\)
\(k=-5\ \ \text{satisfies both equations (infinite solutions)}.\)
\(\Rightarrow B\)
Part of the graph of `y=f(x)` is shown below. The rule `A(k)=k \ sin(k)` gives the area bounded by the graph of `f`, the horizontal axis and the line `x=k`.
--- 2 WORK AREA LINES (style=lined) ---
--- 6 WORK AREA LINES (style=lined) ---
--- 6 WORK AREA LINES (style=lined) ---
a. ` (sqrt(3)pi)/6`
b. `(3sqrt(3) +pi)/6`
c. `k = pi/2`
| a. `A(pi/3)` | `= pi/3sin(pi/3)` | |
| `= pi/3 xx sqrt(3)/2` | ||
| `= (sqrt(3)pi)/6` |
| b. `f(k)` | `= A^{\prime}(k)` | |
| `f(k)` | `=d/dx(k\ sin\ k)` | |
| `= sin\ k + k\ cos\ k` | ||
| `f(pi/3)` | `= sin\ pi/3 + pi/3\ cos\ pi/3` | |
| `= sqrt(3)/2 + pi/3 xx 1/2` | ||
| `= sqrt(3)/2 + pi/6` | ||
| `=(3sqrt(3) +pi)/6` |
| c. Average value | `= (A(k))/k` | |
| `= 1/k(int_0^k f(x) d x)` | ||
| `= 1/k[x\ sin (x)]_0^k` | ||
| `= 1/k[k\ sin (k)] = sin\ k` |
`:.` Average value has a maximum value of 1 when `k = pi/2`
A tilemaker wants to make square tiles of size 20 cm × 20 cm.
The front surface of the tiles is to be painted with two different colours that meet the following conditions:
An example is shown below.
There are two types of tiles: Type A and Type B.
For Type A, the colours on the tiles are divided using the rule `f(x)=4 \sin \left(\frac{\pi x}{10}\right)+a`, where `a \in R`.
The corners of each tile have the coordinates (0,0), (20,0), (20,20) and (0,20), as shown below.
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ii. Find the value of `a` so that a Type A tile meets Condition 1. (1 mark)
--- 2 WORK AREA LINES (style=lined) ---
Type B tiles, an example of which is shown below, are divided using the rule `g(x)=-\frac{1}{100} x^3+\frac{3}{10} x^2-2 x+10`.
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--- 8 WORK AREA LINES (style=lined) ---
a.i. `400` cm²
a.ii. `a = 10`
b. `200` cm²
c. See worked solution
| a.i Area | `= 20 xx 20` | |
| `= 400` cm² |
a.ii `a = 10`
| b. Area | `=\int_0^{20} \frac{-x^3}{100}+\frac{3 x^2}{10}-2 x+10\ d x` | |
| `=\left[\frac{-x^4}{400}+\frac{x^3}{10}-x^2+10 x\right]_0^{20}` | ||
| `=\left[-\frac{20^4}{400}+\frac{20^3}{10}-20^2+10 xx 20\right]-\left[0\right]` | ||
| `= – 400 +800 -400 +200` | ||
| `= 200` cm² |
`:.` The area of the coloured section of the Type B tile is 200 cm² which is half the 400 cm² area of the tile.
| c. |
`f(0)` | `=4 \sin \left(\frac{\pi(0)}{10}\right)+10 = 10` | |
| `f(20)` | `=4 \sin (2 \pi)+10 = 10` | ||
| `g(0)` | `=\frac{-0}{100}+\frac{3(0)}{10}-2(0)+10=10` | ||
| `g(20)` | `=-\frac{8000}{100}+\frac{200}{10}-2(20)+10 = 10` |
→`\ f(0) = f(20) = g(0) = g(20) =10`
`:.` The endpoints for `f(x)` are `(0,10)` and `(20,10)` and for `g(x)` are also `(0,10)` and `(20,10)`.
So the tiles can be placed in any order to make the continuous pattern.