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PHYSICS, M5 EQ-Bank 4 MC

A torque is applied to a nut, using a wrench.
 

Which change will increase the magnitude of applied torque?

  1. Increasing the angle between the applied force and the wrench
  2. Decreasing the angle between the applied force and the wrench
  3. Increasing the distance between the nut and the point of application of the force
  4. Decreasing the distance between the nut and the point of application of the force
Show Answers Only

`C`

Show Worked Solution

→ `tau = rF sin theta`

→ Increasing the distance (`r`) between the point of application of the force and the nut will increase applied torque.

`=>C`

Proof, EXT2 P2 EQ-Bank 11

A sequence is given by the recursive formula

`a_1=10, \ a_(n+1)=3a_n+4`  for  `n>=1`

Using mathematical induction to show the formula for the general term of the sequence is

`a_n=4(3^n)-2`   (3 marks)

Show Answers Only

`text{Proof (See Worked Solution)}`

Show Worked Solution

`text{Prove true for}\ \ n=1:`

`text{LHS}\ =a_1=10`

`text{RHS}\ =4(3^1)-2=10=\ text{LHS}`

`:.\ text{True for}\ \ n=1`
 

`text{Assume true for}\ \ n=k:`

`a_k=4(3^k)-2\ \ text{… (1)}`
 

`text{Prove true for}\ \ n=k+1:`

`text{i.e.}\ a_(k+1)=4(3^(k+1))-2`

`a_(k+1)` `=3a_k+4`  
  `=3[4(3^k)-2]+4`  
  `=4*3^k*3-6+4`  
  `=4(3^(k+1))-2`  
  `=\ text{RHS}`  

 
`:.\ text{True for}\ \ n=k+1`

`:.\ text{Since true for} \ n=1,\ text{by PMI, true for integers} \ n>=1.`

Calculus, EXT1 C3 EQ-Bank 12

Solve  `dy/dx=2x^2-3x`  given that when  `x=3`, `y=-1`.   (2 marks)

Show Answers Only
  1. `y=2/3x^3-3/2x^2-11/2`
Show Worked Solution
`dy/dx` `=2x^2-3x`  
`1\ dy` `=2x^2-3x\ dx`  
`int1\ dy` `=int2x^2-3x\ dx`  
`y` `=2/3x^3-3/2x^2+c`  

 
`text{When}\ \ x=3,\ y=-1:`

`-1` `=2/3 3^3-3/2 3^2+c`  
`c` `=-11/2`  

 
`:.y=2/3x^3-3/2x^2-11/2`

Calculus, EXT1 C3 EQ-Bank 8

A researcher estimates the number of brumbies in a National Park after `t` years can be modelled by the equation

`B(t)=(18\ 000)/(1+4e^(-t))`

  1. Sketch the function `B(t)` over the first four years of the research.   (2 marks)

  2. Calculate when the brumby population should reach 13 000, giving your answer to 2 decimal places.   (1 mark)

  3. Show that  `B^(′)(t)=(72\ 000e^t)/(e^t+4)^2`   (2 marks)

  4. What is the maximum growth rate of the brumby population?   (3 marks)

Show Answers Only
  1.  
     
  2. `2.34\ text{years}`
  3. `text{Proof (See Worked Solutions}`
  4. `4500\ text{brumbies per year}`
Show Worked Solution

i.   

ii.   `text {Find}\ t\ text{when}\ \ B(t)=13\ 000`

`13\ 000` `=(18\ 000)/(1+4e^(-t))`  
`13\ 000(1+4e^(-t))` `=18\ 000`  
`1+4e^(-t)` `=18/13`  
`4e^(-t)` `=5/13`  
`e^(-t)` `=5/52`  
`-t` `=ln(5/52)`  
`t` `=2.34\ text{years (2 d.p.)}`  

 

 iii.   `text{Show}\ \ B^(′)(t)=(72\ 000e^t)/(e^t+4)^2`

`B(t)=18\ 000(1+4e^(-t))^(-1)`

`B^(′)(t)` `=-1*-1*4e^(-t)*18\ 000(1+4e^(-t))^-2`  
  `=(72\ 000)/(e^t(1+4e^(-t))^2)`  
  `=(72\ 000)/(e^t(1+4/e^t)^2)`  
  `=(72\ 000)/(e^t((e^t+4)/e^t)^2)`  
  `=(72\ 000)/(e^t/(e^t)^2*(e^t+4)^2)`  
  `=(72\ 000e^t)/(e^t+4)^2\ \ text{… as required}`  

 

iv.  `B^(′)(t)=72\ 000e^t(e^t+4)^(-2)`

`text{Using product rule:}`

`B^(′′)(t)` `=72\ 000e^t(e^t+4)^(-2)+(-2e^t)(e^t+4)^(-3)72\ 000e^t`  
  `=72\ 000e^t(1/(e^t+4)^2-(2e^t)/(e^t+4)^3)`  
  `=72\ 000e^t((e^t+4-2e^t)/(e^t+4)^3)`  
  `=72\ 000e^t((4-e^t)/(e^t+4)^3)`  

 
`text{Find}\ t\ text{when}\ \ B^(′′)(t)=0:`

`4-e^t` `=0`  
`e^t` `=4`  
`t` `=ln4`  
  `=1.386…\ text{years}`  

 
`text{Checking concavity changes:}`

`text{Since}\ e^t>0, (e^t+4)^3>0\ \ text{for all}\ t:`

`text{At}\ t=1, 4-e^1=1.28>0\ \ =>\ \ B^(′′)(1)>0`

`text{At}\ t=2, 4-e^2=-3.4<0\ \ =>\ \ B^(′′)(2)<0`

 
`B^(′)(ln4)=\ text{Max growth rate}`

`B^(′)(ln4)` `=(72\ 000e^(ln4))/(e^(ln4)+4)^2`  
  `=(72\ 000xx4)/((4+4)^2)`  
  `=4500\ text{brumbies per year}`  

Calculus, EXT1 C3 EQ-Bank 6

The population of Myna birds in a national park is decreasing at a rate proportional to the population at that time.

  1. Write a differential equation that describes the situation.   (1 mark)

  2. If the population was originally 1300 and decreased to 1040 after 5 years, find the expected population after 10 years.  (3 marks)

Show Answers Only
  1. `(dN)/(dt) = -kN`
  2. `832`
Show Worked Solution

i.   `text{Let}\ (dN)/(dt)=\ text{rate of change of bird population at time}\ t\ text{years.}`

`(dN)/(dt) prop N`

`(dN)/(dt) = -kN\ \ (k>0,\ text{decreasing population)}`
 

ii.    `(dN)/(dt)` `=-kN`
  `1/N* (dN)/(dt)` `=-k`
  `int1/N\ dN` `=-intk\ dt`
  `ln absN` `=-kt+c`
  `N` `=e^(-kt+c)`
    `=e^(-kt)*e^c`
    `=Ae^(-kt)\ \ \ text{(where}\ A=e^c)`

 
`text{When}\ \ t=0, N=1300:`

`1300=Ae^0\ \ =>\ \ A=1300`

`N=1300e^(-kt)`
 

`text{When}\ \ t=5, N=1040:`

`1040` `=1300e^(-5k)`  
`e^(-5k)` `=1040/1300`  
`-5k` `=ln(0.8)`  
`k` `=-(ln(0.8))/(5)`  
  `=0.04462…`  

 
`text{Find}\ N\ text{when}\ \ t=10:`

`N` `=1300e^(-0.04462 xx 10)`  
  `=832\ \ text{myna birds}`  

Proof, EXT2 P2 EQ-Bank 2

`n` lines are drawn in a 2-dimensional plane such that no three lines are concurrent and no two lines are parallel.

`S_n` is the number of regions into which these lines divide the plane with the diagram illustrating that `S_3=7`
 

  1. In a similar way, draw diagrams that illustrate `S_1, S_2` and `S_4`.  (1 mark)

  2. Using the results in part (i), make a conjecture about the general formula for `S_n`.  (2 marks)

  3. Use mathematical induction to prove the formula from part (ii).  (3 marks)

Show Answers Only
  1. `text{See Worked Solutions}`
  2. `S_n=(n^2+n+2)/2`
  3. `text{See Worked Solutions}`
Show Worked Solution

i.       `S_1=2`                        `S_2=4`
 
             
 

   `S_4=11`


 

ii.   `text{Consider the pattern above:}`

`S_1=2,\ \ S_2=S_1+2`

`S_3=S_2+3,\ …\ , S_n=S_(n-1)+n`

`S_n` `=S_(n-1)+n`  
  `=S_(n-2)+(n-1)+n`  
  `=S_(n-3)+(n-2)+(n-1)+n`  
  `vdots`  
  `=S_1+(2+3+…+(n-1)+n)`  
  `=S_0+(1+2+…+(n-1)+n)`  
  `=1+(1+2+…+(n-1)+n)`  

 
`=>text{AP where}\ \ a=1, l=n, n=n`

`S_n` `=1+n/2(1+n)`  
  `=(2+n(n+1))/2`  
  `=(n^2+n+2)/2`  

 

iii.   `text{Prove}\ \ S_n=(n^2+n+2)/2\ \ text{for}\ \ n>=0`

`text{If}\ \ n=1`

`text{LHS}\ =S_1=2`

`text{RHS}\ = (1^2+1+2)/2=2=\ text{LHS}`

`:.\ text{True for}\ n=1.`
 

`text{Assume true for}\ \ n=k:`

`text{i.e.}\ S_k=(k^2+k+2)/2`

`text{Prove true for}\ \ n=k+1:`

`text{i.e.}\ S_(k+1)=((k+1)^2+(k+1)+2)/2=(k^2+3k+4)/2`
 

`text{Consider the line}\ d_4\ text{added below that crosses 3 existing lines}`

`text{and creates 4 new regions.}`

`text{Similarly, the line}\ d_(k+1)\ text{will cross}\ k\ text{existing lines and}`

`text{create}\ (k+1)\ text{new regions.}`

`S_(k+1)` `=S_k+k+1`  
  `=(k^2+k+2)/2+k+1`  
  `=(k^2+k+2+2k+2)/2`  
  `=(k^2+3k+4)/2`  
  `=\ text{RHS}`  

 
`:.\ text{True for}\ \ n=k+1`

`:.\ text{Since true for}\ n=1,\ text{by PMI, true for integers}\ n>=1`

Vectors, EXT2 V1 EQ-Bank 14

Use vector methods to find the coordinates of the point that divides the interval joining the points  `A(7,-3,0)`  and  `B(2,2,-10)`  in the ratio `2:3`.  (3 marks)

Show Answers Only

`(5,-1,-4)`

Show Worked Solution

`text{Method 1}`

`text{Let}\ \ underset~c =\ text{position vector of the dividing point}`

`underset~c` `=((7),(-3),(0)) + 2/5((2-7),(2-(-3)),(-10-0))`  
  `=((7),(-3),(0)) + ((-2),(2),(-4))`  
  `=((5),(-1),(-4))`  

 
`text{Method 2}`

`underset~c` `=((2),(2),(-10)) + 3/5((7-2),(-3-2),(0-(-10)))`  
  `=((2),(2),(-10)) + ((3),(-3),(6))`  
  `=((5),(-1),(-4))`  

Vectors, EXT2 V1 EQ-Bank 12

Two planes are flying in directions given by the vectors  `-200underset~i+400underset~j-3underset~k`  and  `300underset~i+250underset~j+underset~k`.

A person in the flight control centre is plotting their paths on a map.

Calculate the acute angle between their projected flight paths, giving your answer correct to one decimal place.  (2 marks)

Show Answers Only

`76.8°`

Show Worked Solution

`text{Let}\ \ underset~a=-200underset~i+400underset~j-3underset~k,\ \ underset~b=300underset~i+250underset~j+underset~k`

`underset~a*underset~b=((-200),(400),(-3))((300),(250),(1))=-60\ 000+100\ 000-3=39\ 997`

`abs(underset~a)=sqrt(200^2+400^2+9)=447.2236…`

`abs(underset~b)=sqrt(300^2+250^2+1)=390.5137…`

`costheta` `=(39\ 997)/(447.2236xx390.5137)`  
  `=0.2291`  
`:.theta` `=76.8°\ \ text{(to 1 d.p.)}`  

Vectors, EXT2 V1 EQ-Bank 9

A parallelogram is formed by joining the points  `P(-2,1,4), Q(1,4,5), R(0,2,3)` and `S(a,b,c)`.

Use vector methods to find `a,b` and `c`.  (2 marks)

Show Answers Only

`a=-3, b=1, c=2`

Show Worked Solution

`text{Opposite sides of a parallelogram are equal and parallel.}`

`=> vec(PQ)=vec(SR)`
 

`vec(PQ)=((1+2),(4-3),(5-4))=((3),(1),(1))`
 

`vec(SR)=((-a),(2-b),(3-c))`
 

`text{Equating coordinates:}`

`-a=3\ \ =>\ \ a=-3`

`2-b=1\ \ =>\ \ b=1`

`3-c=1\ \ =>\ \ c=2`

Vectors, EXT2 V1 EQ-Bank 7

In triangle `ABC`, `M` is the midpoint of `AC` and `N` is the midpoint of `AB`.

Use vector methods to prove that

  1. `MN=1/2CB`   (2 marks)

  2. `MN` is parallel to `CB`   (1 mark)

Show Answers Only
  1. `text(See Worked Solution)`
  2. `text(See Worked Solution)`
Show Worked Solution

i.   
     

`vec(AC)+vec(CB)+vec(BA)=0\ \ \ text{(resultant vector ends at starting point)}`

`vec(CB)=-(vec(AC)+vec(BA))`
 

`text(S)text(ince)\ M\ text (and)\ N\ text(are midpoints:)`

`vec(MN)` `=-1/2vec(AC)-1/2vec(BA)`  
  `=-1/2(vec(AC)+vec(AB))`  
  `=1/2vec(CB)\ \ text(… as required)`  

 

ii.   `text{If}\ \ vec(u) = kvec(v)\ \ (k\ text{scalar})\ \ =>\ \ vec(u)\ text{||}\ vec(v)`

`vec(MN)=1/2vec(CB)\ \ text{(see (i))`

`:.MN\ text{||}\ RCB`

Vectors, EXT2 V1 EQ-Bank 6

Use vector methods to find the coordinates of the point that divides the interval joining the points  `A(-1,3,2)`  and  `B(7,-1,-6)`  in the ratio `1:3`.  (3 marks)

Show Answers Only

`(1,2,0)`

Show Worked Solution

`text{Method 1}`

`text{Let}\ \ underset~c =\ text{position vector of the dividing point}`

`underset~c` `=((-1),(3),(2)) + 1/4((7-(-1)),(-1-3),(-6-2))`  
  `=((-1),(3),(2)) + ((2),(-1),(-2))`  
  `=((1),(2),(0))`  

 
`text{Method 2}`

`underset~c` `=((7),(-1),(-6)) + 3/4((-1-7),(3-(-1)),(2-(-6)))`  
  `=((7),(-1),(-6)) + ((-6),(3),(6))`  
  `=((1),(2),(0))`  

Vectors, EXT2 V1 EQ-Bank 5

Use two vector methods to locate the midpoint of the interval joining the points  `A(3,-2,1)`  and  `B(5,4,-3)`.  (3 marks)

Show Answers Only

`(4,-1,-1)`

Show Worked Solution

`text{Method 1}`

`text{Let}\ \ underset~c =\ text{position vector of the midpoint}`

`underset~c` `=((3),(-2),(1)) + 1/2((5-3),(4-(-2)),(-3-1))`  
  `=((3),(-2),(1)) + ((1),(3),(-2))`  
  `=((4),(1),(-1))`  

 
`text{Method 2}`

`underset~c` `=((5),(4),(-3)) + 1/2((3-5),(-2-4),(1-(-3)))`  
  `=((5),(4),(-3)) + ((-1),(-3),(2))`  
  `=((4),(1),(-1))`  

Vectors, EXT2 V1 EQ-Bank 3

If  `underset ~a = 3 underset ~i-underset ~j`  and  `underset ~b = −2 underset ~i + 6 underset ~j + 2underset ~k`

  1. Calculate  `underset ~a-1/2underset ~b`   (2 marks)

  2. Find  `hat underset ~b`   (2 marks)

Show Answers Only
  1. `((4),(-4),(-1))`
  2.  `hat underset~b=((-sqrt11)/11, (3sqrt11)/11, sqrt11/11)`
Show Worked Solution
i.    `underset~a-1/2underset~b` `=((3),(-1),(0))-1/2((-2),(6),(2))`
    `=((3),(-1),(0))-((-1),(3),(1))`
    `=((4),(-4),(-1))`

 

ii.    `hat underset~b = underset~b/{abs(underset~b)}`

`abs(underset~b)=sqrt((-2)^2+6^2+2^2)=sqrt44=2sqrt11`

`hat underset~b` `=1/(2sqrt11)(-2,6,2)`  
  `=((-1)/sqrt11, 3/sqrt11, 1/sqrt11)`  
  `=((-sqrt11)/11, (3sqrt11)/11, sqrt11/11)`  

BIOLOGY, M7 2014 HSC 5 MC

In which of the following cases would bacteria be described as pathogens?

  1. Bacteria reducing lung function in mammals
  2. Bacteria in the human gut assisting digestion
  3. Bacteria producing insulin as a result of genetic engineering
  4. Bacteria in the mouth preventing growth of harmful bacteria
Show Answers Only

`A`

Show Worked Solution

→ A pathogen is a biological agent of disease.

→ Bacteria ‘A’ is the only one which fits the criteria of a pathogen.

`=>A`

PHYSICS, M5 EQ-Bank 5 MC

An object is projected upwards from the ground, and follows a path as represented in the diagram.
 

Which of the following describes the projectile's horizontal and vertical acceleration at point `Y` ?

  1. Both the horizontal and vertical acceleration are zero.
  2. Both the horizontal and vertical acceleration are `9.8 \ text{m s}^(-2)`.
  3. The horizontal acceleration is `9.8 \ text{m s}^(-2)` and the vertical acceleration is zero.
  4. The horizontal acceleration is zero and the vertical acceleration is `9.8 \ text{m s}^(-2)`.
Show Answers Only

`D`

Show Worked Solution

→ There are no horizontal forces acting on the ball throughout its flight, so its horizontal acceleration is always zero.

→ The ball experiences a net downwards force due to gravity. This results in a constant vertical acceleration of `9.8  text{m s}^(-2)` downwards.

`=>D`

PHYSICS, M5 EQ-Bank 1 MC

Some students were testing the hypothesis that launching a projectile at an angle of 45° will give the maximum horizontal range.

Which experimental setup will best test the hypothesis?
 

Show Answers Only

`C`

Show Worked Solution

By Elimination:

→ In this experiment horizontal range is the dependent variable and launch angle is the independent variable. So, launch angle must be varied (eliminate `A`).

→ To be a valid experiment, the independent variable, i.e. the launch angle, must be the only variable which changes (eliminate `D`).

→ Between `B` and `C`, `C` has a larger range of angles tested, whereas `B` uses too narrow a range of angles to make a valid conclusion.

`=>C`

ENGINEERING, AE 2017 HSC 6 MC

The diagram shows an aerofoil.
 

Which condition needs to be achieved for lift to occur?

  1. Pressure 1<Pressure 2
  2. Pressure 1= Pressure 2
  3. Pressure 1> Pressure 2
  4. Pressure 1+ Pressure 2=0
Show Answers Only

`A`

Show Worked Solution

→ For a net upwards force, the force from pressure below (pushing up) must exceed the force from pressure above (pushing down).

→ Therefore Pressure 1<Pressure 2.

`=A>`

ENGINEERING, CS 2018 HSC 23b

The steel used in the chassis members was tested.

The load–extension graph represents the data collected during the testing of a specimen of the steel.
 

Before testing, the specimen was 1020 mm long with a cross-sectional area of 100 mm².

  1. Calculate Young's modulus for this steel.   (4 marks)
  1. Describe the physical changes that occur in the specimen tested in part (i) when a 20 kN load is applied and then removed, compared to when a 30 kN load is applied and then removed.   (2 marks)
Show Answers Only

i.   Young’s modulus

`F = 20 xx 10^3\ text{N}, l = 1020\ text{mm},  e = 1\ text{mm},  text{A} = 100\ text{mm}^2`

`E` `=(Fl)/(eA)`  
  `=(20 xx 10^3 xx1020)/(1 xx 100)`  
  `=204 xx 10^3`  
  `=204\ text{GPa}`  

 

ii.   → Elastic deformation is produced by the 20 kN load.

→ After initial stretching the specimen returns to its original length.

→ Plastic deformation is produced by the 30 kN load.

→ The specimen stays deformed subsequent to release.

Show Worked Solution

i.   Young’s modulus

`F = 20 xx 10^3\ text{N}, l = 1020\ text{mm},  e = 1\ text{mm},  text{A} = 100\ text{mm}^2`

`E` `=(Fl)/(eA)`  
  `=(20 xx 10^3 xx1020)/(1 xx 100)`  
  `=204 xx 10^3`  
  `=204\ text{GPa}`  

 


♦ Mean mark (i) 51%.

ii.  → Elastic deformation is produced by the 20 kN load.

→ After initial stretching the specimen returns to its original length.

→ Plastic deformation is produced by the 30 kN load.

→ The specimen stays deformed subsequent to release.

ENGINEERING, PPT 2018 HSC 21b

Outline the benefits of using electric motors to power self-driving vehicles.   (3 marks)

Show Answers Only

Successful engines should include three of the following:

→ Reduced amount of tailpipe emissions through the use of renewable energy as the power source.

→ Lighter engine construction produces a better power to weight ratio.

→ Quieter engines reduce noise pollution.

→ Technology enabling simpler integration into an automated vehicle control system.

→ Less moving parts in electric motors mean they break down less often and need less maintenance.

Show Worked Solution

Successful engines should include three of the following:

→ Reduced amount of tailpipe emissions through the use of renewable energy as the power source.

→ Lighter engine construction produces a better power to weight ratio.

→ Quieter engines reduce noise pollution.

→ Technology enabling simpler integration into an automated vehicle control system.

→ Less moving parts in electric motors mean they break down less often and need less maintenance.

ENGINEERING, AE 2018 HSC 17 MC

Aircraft skins can be constructed using either fibre metal laminate (FML) or sheet aircraft-grade aluminium alloy.

FML is preferred in this application because it has

  1. higher density and lower Young's modulus.
  2. higher density and improved fatigue resistance.
  3. higher strength-to-weight ratio and lower Young's modulus.
  4. higher strength-to-weight ratio and improved fatigue resistance.
Show Answers Only

`D`

Show Worked Solution

→ Higher density and lower Young’s modulus are both negative material properties for aircraft skins, as these skins should be light (lower density) and rigid (higher stiffness/Young’s modulus).

→ Additionally, fatigue resistance is important as aircraft skins are exposed to varying air pressures.

`=>D`

ENGINEERING, PPT 2018 HSC 8 MC

In which of the following do all of the processes require plastic deformation to achieve a final shape?

  1. Brazing, casting, rolling
  2. Brazing, soldering, welding
  3. Extruding, casting, forging
  4. Extruding, pressing, rolling
Show Answers Only

`D`

Show Worked Solution

→ Brazing, casting, soldering and welding involve metal in liquid form and therefore do not require plastic deformation. (Cannot be `A`, `B` or `C`)

`=>D`

ENGINEERING, PPT 2018 HSC 7 MC

An arrangement of resistors is shown.
 

What is the total resistance of this arrangement of resistors?

  1. `33 Omega`
  2. `50 Omega`
  3. `150 Omega`
  4. `300 Omega`
Show Answers Only

`C`

Show Worked Solution
`R_(text{total})` `=R_(text{parallel}) + 100 Omega`  
`1/(R_(text{parallel}))` `= 1/R_1 + 1/R_2`  
  `= 2/100`  
  `= 1/50`  
`R_(text{parallel})` `= 50 Omega`  

 

`:. R_(text{total})` `= 50 + 100`  
  `= 150 Omega`  

  
`=>C`

ENGINEERING, CS 2018 HSC 5 MC

Two types of bridge are shown.
 

What are the two types of bridge design shown?

  1. Suspension bridge and masonry arch
  2. Suspension bridge and masonry beam
  3. Reinforced concrete arch and masonry arch
  4. Reinforced concrete arch and masonry beam
Show Answers Only

`C`

Show Worked Solution

 → Both bridges are arch beams, therefore C is correct.

 → In suspension bridges, the deck is suspended from above by vertical cables.

 → Beam bridges are a simple flat beam from one side to another, neither of which are shown here.

`=>C`

ENGINEERING, TE 2018 HSC 21d

Digital logic controls a self-driving vehicle's brakes.
 

Brakes will be applied when all of the following conditions are met:

    • the motor is on
    • the vehicle is in motion
    • either sensor 1 or sensor 2 is activated.

Explain how the logic gates, labelled 1, 2 and 3 in the circuit below, control the vehicle's brakes.   (3 marks)
 

Show Answers Only
  1. Logic gate 1 – AND – both inputs must be ON for ON output
  2. Logic gate 2 – OR – either input ON to produce ON output
  3. Logic gate 3 – AND – both inputs must be ON for ON output (ie brakes are applied)
Show Worked Solution
  1. Logic gate 1 – AND – both inputs must be ON for ON output
  2. Logic gate 2 – OR – either input ON to produce ON output
  3. Logic gate 3 – AND – both inputs must be ON for ON output (ie brakes are applied)

BIOLOGY, M8 2019 HSC 33c

A large epidemiological study was conducted. It used historical data to investigate the association between Herpes simplex virus (HSV) infection and dementia. Dementia is caused by a variety of brain illnesses. Alzheimer's disease is the most common cause of dementia.

The study used the records of 8362 patients with HSV infection and 25086 randomly selected sex- and age-matched control patients without HSV infection. Some of the patients with HSV had been treated with antiviral medication.

The graph below shows some results of the study.
 

  1. Describe the trends shown in the data.   (3 marks)
Show Answers Only

→ The graph clearly shows that individuals with untreated HSV are at a greater risk of developing Alzheimer’s. While people without HSV or treated HSV remain relatively low up to 10 years, HSV patients can have 10 to 15 times the likelihood of developing Alzheimer’s, a trend which increases with age/time with HSV.

→ The treated HSV patients remain relatively low and almost identical to the individuals without HSV until 10 years where there is a sharp increase. However, it is still half the risk of untreated patients.

→ People without HSV have an incredibly low likelihood of obtaining Alzheimer’s, with only a very small increase in the 10 year follow up. 

Show Worked Solution

Data Trends:

→ The graph clearly shows that individuals with untreated HSV are at a greater risk of developing Alzheimer’s. While people without HSV or treated HSV remain relatively low up to 10 years, HSV patients can have 10 to 15 times the likelihood of developing Alzheimer’s, a trend which increases with age/time with HSV.

→ The treated HSV patients remain relatively low and almost identical to the individuals without HSV until 10 years where there is a sharp increase. However, it is still half the risk of untreated patients.

→ People without HSV have an incredibly low likelihood of obtaining Alzheimer’s, with only a very small increase in the 10 year follow up. 

ENGINEERING, TE 2019 HSC 27a

A telecommunications tower with repeater transmitters is shown. The tower is assembled from many individual parts.
 

Explain why detailed drawings are used in the design and manufacture of these individual parts.  (2 marks)

Show Answers Only

→ A scaled ‘Detail Drawing’ is required for a Structural Engineer to communicate information regarding individual parts.

→ To ensure accurate manufacture of parts that fit together during assembly, the detailed drawing would use a suitable scale so all details are apparent (eg 2:1, 5:1 and 10:1).

→ There is a high risk of inaccurately manufactured parts if detailed drawings are not provided.

Show Worked Solution

→ A scaled ‘Detail Drawing’ is required for a Structural Engineer to communicate information regarding individual parts.

→ To ensure accurate manufacture of parts that fit together during assembly, the detailed drawing would use a suitable scale so all details are apparent (eg 2:1, 5:1 and 10:1).

→ There is a high risk of inaccurately manufactured parts if detailed drawings are not provided.

ENGINEERING, TE 2019 HSC 22a

A telecommunications engineer has designed a tower that is to support two mobile repeater transmitters. It is to be located in an urban community.
 

Outline responsibilities the engineer has when placing the tower within a local community.   (3 marks)

Show Answers Only

Answers could include 3 of the following points:

→ Minimise health risks, so tower not erected near high density housing, childcare centres or schools.

→ Designed so visual pollution reduced.

→ Positioned so best possible signals are achieved and dead spots are minimised.

→ Easy accessibility for maintenance without consequences to the community.

→ Construction completed with least possible disruption to the community.

Show Worked Solution

Answers could include 3 of the following points:

→ Minimise health risks, so tower not erected near high density housing, childcare centres or schools.

→ Designed so visual pollution reduced.

→ Positioned so best possible signals are achieved and dead spots are minimised.

→ Easy accessibility for maintenance without consequences to the community.

→ Construction completed with least possible disruption to the community.

ENGINEERING, CS 2019 HSC 11 MC

The table shows materials that have been used to build civil structures over time.

Which row of the table shows the use of the materials in the correct historical order?
 

Show Answers Only

`A`

Show Worked Solution

By Elimination:

→ Stainless steel must have been used after mild steel as it is an alloy of mild steel (not `C` or `D`)

→ Stone was used before iron as it did not require any processes to be formed (not `B`)

`=>A`

ENGINEERING, PPT 2019 HSC 7 MC

A box sits on a horizontal surface. The box begins to slip when this surface is tilted to 28 degrees.

What is the coefficient of friction between the box and the surface?

  1. 0.280
  2. 0.469
  3. 0.532
  4. 0.883
Show Answers Only

`C`

Show Worked Solution

`mu = tan(phi) = tan28° = 0.532`

`=>C`

PHYSICS, M8 2015 HSC 33d

The position of the Sun, star `W` and star `Z` are shown on the H-R diagram.
 

The curves `A` and `B` show intensity versus frequency for star `W` and the Sun, measured from the same distance.
 

  1. Identify which curve (`A` or `B`) represents star `W` and justify your choice.   (2 marks)
  1. Account for differences between stars `W` and `Z` that can be deduced from the H-R diagram.   (3 marks)
Show Answers Only

i.    → Curve A represents star `W`.

→ `W` is hotter so will emit more energy overall, and peak frequency will be higher.
 

ii.   Differences displayed in H-R graph:

→ Star `W` lies in the main sequence and is therefore fusing hydrogen to helium, most likely via CNO cycle as it is a large dense star.

→ Star `Z` is past main sequence and is therefore fusing larger elements.

→ Since star `Z` is cooler than `W` (refer to its H-R diagram location ) but has similar luminosity, we can deduce it is much larger than `W`.
 

Other possible answers could include:

→ Differences in fuel source, size and temperature of the stars.

Show Worked Solution

i.    → Curve A represents star `W`.

→ `W` is hotter so will emit more energy overall, and peak frequency will be higher.
 

ii.   Differences displayed in H-R graph:

→ Star `W` lies in the main sequence and is therefore fusing hydrogen to helium, most likely via CNO cycle as it is a large dense star.

→ Star `Z` is past main sequence and is therefore fusing larger elements.

→ Since star `Z` is cooler than `W` (refer to its H-R diagram location ) but has similar luminosity, we can deduce it is much larger than `W`.
 

Other possible answers could include:

→ Differences in fuel source, size and temperature of the stars.

PHYSICS, M8 2016 HSC 34ai

Identify the TWO types of nucleon and state ONE difference between them.   (2 marks)

Show Answers Only

→ Nucleon types: Neutrons and protons.

→ Difference: Protons are positively charged whereas neutrons have no charge.

Show Worked Solution

→ Nucleon types: Neutrons and protons.

→ Difference: Protons are positively charged whereas neutrons have no charge.

BIOLOGY, M8 2018 HSC 31a

  1. Identify TWO structures that refract light as it passes through the eye.   (2 marks)

  2. The diagram shows the human eye. The two lines labelled `A` and `B` represent two beams of light passing through the eye and stimulating different areas of the retina.   

 

  1. The visual perception will be different at the two stimulated areas.
  2. Identify TWO of these differences.  (2 marks)

Show Answers Only

“

Show Worked Solution

i.    Cornea and lens

ii.   Differences in visual perception at `A` and `B`.

→ At the fovea (where `A` strikes), there is a high concentration of cones, so more detail will be detected and better colour perceived than at the periphery.

→ At the periphery (where `B` strikes) there is low visual acuity (detail) and less colour perception, however, there is good distinction between black and white due to the high proportion of rods.


♦♦ Mean mark (ii) 32%.

BIOLOGY, M8 2018 HSC 21

  1. Identify TWO responses of a named endotherm to a decrease in body temperature.  (2 marks)

  2. Outline the role of the nervous system of an endotherm in maintaining homeostasis when its body temperature changes.  (2 marks)

Show Answers Only

a.   Vasoconstriction and shivering.

b.   Body temperature maintenance in endotherms:

→ This is achieved via negative feedback loops.

→ Temperature receptors in the brain and skin detect changes in body temperature.

→ The central nervous system receives a signal via the receptors.

→ Muscles or glands (effectors) then receive nerve signals sent from the central nervous system.

Show Worked Solution

a.   Vasoconstriction and shivering.
 

b.   Body temperature maintenance in endotherms:

→ This is achieved via negative feedback loops.

→ Temperature receptors in the brain and skin detect changes in body temperature.

→ The central nervous system receives a signal via the receptors.

→ Muscles or glands (effectors) then receive nerve signals sent from the central nervous system.

BIOLOGY, M5 2017 HSC 19 MC

A zebronkey hybrid is the result of crossing a male zebra which has 44 chromosomes with a female donkey which has 62 chromosomes.

How many chromosomes will the zebronkey have?

  1. 53
  2. 75
  3. 84
  4. 106
Show Answers Only

`A`

Show Worked Solution

→ A haploid set of 22 chromosomes came from the zebra and 31 came from the donkey.

`=>A`

BIOLOGY, M5 2017 HSC 12 MC

What is the probability of producing a tall pea plant when a heterozygous tall pea plant is crossed with a homozygous short pea plant?

  1. 0%
  2. 50%
  3. 75%
  4. 100%
Show Answers Only

`B`

Show Worked Solution

→ Half the gametes produced by the heterozygous pea will have the T allele and the other half the t.

→ The homozygous short produces only t that are dominated by the T.

`=>B`

BIOLOGY, M7 2017 HSC 4 MC

What is the role of lymphocytes in the body?

  1. They fight infection.
  2. They initiate blood clotting.
  3. They transport oxygen around the body.
  4. They transport carbon dioxide around the body.
Show Answers Only

`A`

Show Worked Solution

→ Lymphocytes (B and T cells) protect the body from pathogens by coordinating the immune response.

`=>A`

BIOLOGY, M5 2016 HSC 26

Students conducted preliminary experiments across different species to analyse their DNA base composition.

The table shows the experimental data collected.

\begin{array}{|c|c|c|}
\hline \rule{0pt}{2.5ex}\textit{Species} \rule[-1ex]{0pt}{0pt}& \textit{% Adenine} & \textit{% Guanine} \\
\hline \rule{0pt}{2.5ex}\text{A} \rule[-1ex]{0pt}{0pt}& 38 & 12 \\
\hline \rule{0pt}{2.5ex}\text{B} \rule[-1ex]{0pt}{0pt}& 26 & 22 \\
\hline \rule{0pt}{2.5ex}\text{C} \rule[-1ex]{0pt}{0pt}& 8 & 40 \\
\hline \rule{0pt}{2.5ex}\text{D} \rule[-1ex]{0pt}{0pt}& 20 & 32 \\
\hline \rule{0pt}{2.5ex}\text{E} \rule[-1ex]{0pt}{0pt}& 33 & 18 \\
\hline
\end{array}

 

  1. On the grid below, plot the % Adenine vs % Guanine of the species analysed AND draw a suitable line of best fit.   (3 marks)
     
     

     
  2. Identify the relationship shown by the data.   (1 mark)

  3. Explain the relationship shown by the data.   (3 marks)

Show Answers Only

a.  

b.  As % Adenine increases, the % Guanine decreases.
  

c.    Explanation of data relationship:

→ Adenine and Thymine are complementary base pairs. Likewise with Guanine and Cytosine.

→ It would therefore be expected that as the percentage of adenine increases, the percentage of thymine would also increase.

→ Adenine + Thymine + Cytosine + Guanine = 100%

→ It follows that as adenine increases the amount of guanine should decrease.

Show Worked Solution

a.  

b.  As % Adenine increases, the % Guanine decreases.
  

c.    Explanation of data relationship:

→ Adenine and Thymine are complementary base pairs. Likewise with Guanine and Cytosine.

→ It would therefore be expected that as the percentage of adenine increases, the percentage of thymine would also increase.

→ Adenine + Thymine + Cytosine + Guanine = 100%

→ It follows that as adenine increases the amount of guanine should decrease.


♦♦♦ Mean mark (c) 28%.

BIOLOGY, M7 2016 HSC 24

Name an infectious disease and explain how ONE host response is a defence adaptation.  (3 marks)

Show Answers Only

Exemplar solution:

→ A primary immune response is triggered when a person first contracts chicken pox – an infectious disease.

→ Activated B and T cells reproduce in large numbers to fight and destroy the pathogen.

→ The host survives.

→ Subsequent infection with the same pathogen results in an increased secondary immune response.

Show Worked Solution

Exemplar solution:

→ A primary immune response is triggered when a person first contracts chicken pox – an infectious disease.

→ Activated B and T cells reproduce in large numbers to fight and destroy the pathogen.

→ The host survives.

→ Subsequent infection with the same pathogen results in an increased secondary immune response.

CHEMISTRY, M7 2018 HSC 10 MC

Which row of the table correctly matches the reaction type with the reactant(s), catalyst and product(s)?
 

Show Answers Only

`D`

Show Worked Solution

→ The dehydration of an alkanol \(\ce{(C2H5OH)}\) uses a concentrated acid catalyst to produce an alkene \(\ce{(C2H4)}\) and water.

`=>D`

CHEMISTRY, M8 2018 HSC 28

A camp stove using butane as a fuel was used to heat a pot of water inside a small tent. Poisonous carbon monoxide `(text{CO})` gas can be released from these stoves.
 

An investigation was carried out to determine the carbon monoxide concentration in the tent when the clearance height of the pot above the flame was altered. The results are shown in the table.

\begin{array} {|l|c|c|c|c|}
\hline \text{Clearance height (mm)} & 35 & 40 & 45 & 50 \\
\hline \text{CO concentration (ppm)} & 120 & 87 & 50 & 18\\
\hline \end{array}

  1. Construct a graph of the data on the grid.   (3 marks)

  1. Air containing a `(text{CO})` concentration above 30 ppm is considered unsafe to breathe.  
  2. What is the minimum clearance height at which the pot should be placed?   (1 mark)

  3. Increasing the clearance height decreases the efficiency of the stove according to the following table. 

\begin{array} {|l|c|c|c|c|}
\hline \text{Clearance height (mm)} & 35 & 40 & 45 & 50 \\
\hline \text{Efficiency (%)} & 90 & 70 & 50 & 30\\
\hline \end{array}

  1. A bushwalker only has 15.0 g of butane with which to heat 1.0 L of water with a starting temperature of 20°C.
  2. Calculate the highest temperature of the water that could safely be achieved in the tent. (Molar heat of combustion of butane: `DeltaH_(c)` = 2877 kJ mol ¯1)  (4 marks)

Show Answers Only

a.   
     

b.  48 mm

c.   91.1°C

Show Worked Solution

a.   
     

b.  From the graph, the minimum height above the flame is 48 mm.

c.    → The lowest safe distance = 48 mm (part (b)).

→ Fuel efficiency is 40% at 48 mm 

→ `DeltaH_(c) = 0.4 xx 2877 = 1151\ text{kJ mol}^{-1}`

\[\ce{n(C4H10) = \frac{m}{MM} = \frac{15}{4 \times 12.01 + 10 \times 1.008} = \frac{15}{58.12} = 0.258 mol}\]

\(\ce{Energy (C4H10) = 0.258 \times 1151 = 297 kJ}\)

`q` `=mC DeltaT`  
`297\ 000` `=1.0 xx 4.18 xx 10^3 xx Delta T`  
`Delta T` `=(297\ 000)/(4.18 xx 10^3)`  
  `=71.1°text{C}`  

 
`:.` Highest temperature of water = 20.0 + 71.1 = 91.1°C


Mean mark (c) 54%.

CHEMISTRY, M7 2018 HSC 21

Ethylene can be readily transformed into many useful products.

  1. What is the name of the industrial process by which ethylene is obtained from long chain alkanes?   (1 mark)

  2. Ethylene can be converted into vinyl chloride.
  3. Draw structural formulae for vinyl chloride and its polymer, polyvinyl chloride.   (2 marks)

Show Answers Only

a.   Cracking

b.   Vinyl chloride:


      

Polyvinyl chloride:
 
     

Show Worked Solution

a.   Cracking

b.   Vinyl chloride:


      

Polyvinyl chloride:
 
     

BIOLOGY, M7 2018 HSC 11 MC

The following plants were presented to a quarantine office in Australia as part of a shipment of plants entering Australia for the plant nursery trade.


 

Which of the following is a decision that the quarantine office is likely to make?

  1. Plant `W` can enter Australia as it looks like it has 'black spot' which already occurs in Australia.
  2. Plant `X` can enter Australia as it is unlikely the disease it has will transfer to Australian species.
  3. Plant `Y` cannot enter Australia as it has a disease caused by shortage of soil magnesium.
  4. Plant `Z` cannot enter Australia because its appearance suggests it may be carrying live insects.
Show Answers Only

`D`

Show Worked Solution

→ The aim of quarantine is to prevent any pathogens from entering the country.

→ Any plant that appears to contain live insects has a chance of carrying international diseases, and will therefore be quarantined.

`=>D`

ENGINEERING, CS 2022 HSC 23a

The image shows a laminated veneer lumber (LVL) beam that is used to span long distances in buildings.
 

Give reasons for using LVL instead of a steel beam as the supporting member in a building.   (2 marks)

Show Answers Only

Possible reasons include:

→ LVL has higher strength to weight ratio

→ Easier to attach to other timber framing members

→ Uses timber otherwise thrown away as waste

→ Can use defective timber as surrounding layers will support defects

→ Cheaper

→ Easier to colour

Show Worked Solution

Possible reasons include:

→ LVL has higher strength to weight ratio

→ Easier to attach to other timber framing members

→ Uses timber otherwise thrown away as waste

→ Can use defective timber as surrounding layers will support defects

→ Cheaper

→ Easier to colour

CHEMISTRY, M5 2016 HSC 28

A mixture of carbon monoxide, chlorine and phosgene \(\ce{(COCl_2)}\) gases was placed in a closed container. The concentrations of the gases were monitored over time.
 

  1. At what time does the system first reach equilibrium? Justify your answer.   (2 marks)

  2. At four minutes, the temperature of the container was increased.
  3. Explain, with reference to the graph, whether the decomposition of \(\ce{COCl_2}\) into \(\ce{CO}\) and \(\ce{Cl_2}\) is exothermic or endothermic.   (3 marks)

Show Answers Only

a.    At two minutes (where the concentrations stop changing)

b.    \(\ce{CO(g) + Cl2(g) \rightleftharpoons COCl2(g)}\)

→ From the graph, when the temperature is increased, the \(\ce{COCl2}\) concentration decreases while \(\ce{CO}\) and \(\ce{Cl2}\) concentrations increases.

→ The reaction is countering the increase in temperature by shifting to the left and absorbing heat (Le Chatelier’s principle).

→ Therefore the decomposition of \(\ce{COCl2(g)}\) is endothermic.

Show Worked Solution

a.    At two minutes (where the concentrations stop changing)

b.    \(\ce{CO(g) + Cl2(g) \rightleftharpoons COCl2(g)}\)

→ From the graph, when the temperature is increased, the \(\ce{COCl2}\) concentration decreases while \(\ce{CO}\) and \(\ce{Cl2}\) concentrations increases.

→ The reaction is countering the increase in temperature by shifting to the left and absorbing heat (Le Chatelier’s principle).

→ Therefore the decomposition of \(\ce{COCl2(g)}\) is endothermic.

CHEMISTRY, M7 2016 HSC 22

This apparatus was set up to produce methyl butanoate.
 

  1. Identify a safety issue in this experiment.   (1 mark)

  2. Using structural formulae, write the equation for the production of methyl butanoate.   (2 marks)

  3. Justify the use of apparatus `X` in this experiment.   (2 marks)

Show Answers Only

a.   Flame could ignite one of reagents which is flammable.

b.   
     

c.    → Esterification is a relatively slow reaction.

→ Heating the reaction makes it go faster. However, the low boiling points of the reactants make them volatile as they readily convert into gas.

→ The cooling condenser `X` prevents the gas reactants from escaping the experiment by condensing them back into the reaction mixture. This process allows the reaction to proceed at higher temperatures.

Show Worked Solution

a.   Flame could ignite one of reagents which is flammable.
 

b.   
     


 


♦ Mean mark (b) 52%.

c.    → Esterification is a relatively slow reaction.

→ Heating the reaction makes it go faster. However, the low boiling points of the reactants make them volatile as they readily convert into gas.

→ The cooling condenser `X` prevents the gas reactants from escaping the experiment by condensing them back into the reaction mixture. This process allows the reaction to proceed at higher temperatures.


♦♦♦ Mean mark (c) 14%.

CHEMISTRY, M7 2016 HSC 17 MC

A polymer has the following structure.
 

Which of the following represents the monomer from which this polymer can be produced?
 

 

Show Answers Only

`D`

Show Worked Solution

→ Break the polymer at every second \(\ce{C–C}\) bond (yields identical sections)

→ Adjust single carbon bond to \(\ce{C=C}\) bond in monomer

`=>D`

ENGINEERING, AE 2022 HSC 8 MC

It is appropriate to produce a half development of a transition piece when the piece

  1. is very large.
  2. is symmetrical.
  3. is very complex.
  4. needs to be produced quickly.
Show Answers Only

`B`

Show Worked Solution

→ Half development of a transition piece is appropriate when it is symmetrical.

`=>B`

CHEMISTRY, M6 2015 HSC 21

  1. Outline a suitable method to prepare a natural indicator.   (2 marks)

  2. How could a natural indicator be tested?   (2 marks)

Show Answers Only

a.    Methodology:

→ Collect plant material that is a natural indicator of pH. Examples include rose petals and red cabbage.

→ Cut the coloured parts into small pieces.

→ Place material into a beaker with water and boil until the solution becomes coloured.

→ Allow the mixture to cool at room temperature.

→ Decant the liquid into a container, leaving the solid behind.
 

b.    → Prepare test tubes of various acids and bases (pH of each is known).

→ Add some of the indicator to each test tube.

→ Record the natural indicator colour of each example and whether it differentiates between acids and bases and their concentrations.

Show Worked Solution

a.    Methodology:

→ Collect plant material that is a natural indicator of pH. Examples include rose petals and red cabbage.

→ Cut the coloured parts into small pieces.

→ Place material into a beaker with water and boil until the solution becomes coloured.

→ Allow the mixture to cool at room temperature.

→ Decant the liquid into a container, leaving the solid behind.
 

b.    → Prepare test tubes of various acids and bases (pH of each is known).

→ Add some of the indicator to each test tube.

→ Record the natural indicator colour of each example and whether it differentiates between acids and bases and their concentrations.

CHEMISTRY, M8 2015 HSC 18-19 MC

Question 18

How could the reliability of the analysis of the pond water be improved?

  1. Analyse more samples from the same pond
  2. Use 50 mL of distilled water as a control sample
  3. Analyse samples from different ponds on the site
  4. Remove other contaminants from the sample before the analysis

 
Question 19

What was the concentration of lead ions in the sample?

  1. `5.0 × 10^{-3} \ text{mol L}^(-1)`
  2. `5.8 × 10^{-3} \ text{mol L}^(-1)`
  3. `9.3 × 10^{-3} \ text{mol L}^(-1)`
  4. `10.7 × 10^{-3} \ text{mol L}^(-1)`
Show Answers Only

`18.  A`

`19.  C`

Show Worked Solution

Question 18

`=>A`
 

Question 19

\[\ce{n(PbCl2) = \frac{0.13}{207.2 + 2 \times 35.45} = \frac{0.13}{278.1} = 4.67 \times 10^{-4} mol}\]

\(\ce{n(Pb^2+) = n(PbCl2) = 4.67 \times 10^{-4} mol}\)

\[\ce{[Pb^2+] = \frac{4.67 \times 10^{-4}}{0.050} = 9.3 \times 10^{-3} mol L^{-1}}\]

`=>C`


♦ Mean mark (Q19) 52%.

BIOLOGY, M7 2015 HSC 25

A group of students wanted to test whether water purifying tablets were effective in making creek water free from bacteria.

They conducted an experiment using a water sample collected from the creek and found that the tablets were effective.

  1. Describe a means of addressing ONE identified hazard relevant to this investigation.   (2 marks)

  2. Illustrate the results of this experiment in diagrammatic form.
  3. Use labels to clearly identify the data collected.   (3 marks)
     
     

Show Answers Only

a.   Successful answers could include one of the following:

→ A pathogenic microbe might be cultured during the process.

→ Post experiment, agar plates must be heated under high pressure to kill any microbes cultured before disposal.
  

b.   Results of experiment:

Show Worked Solution

a.   Successful answers could include one of the following:

→ A pathogenic microbe might be cultured during the process.

→ Post experiment, agar plates must be heated under high pressure to kill any microbes cultured before disposal.
  

b.   Results of experiment:

BIOLOGY, M7 2015 HSC 19-20 MC

Refer to the following information to answer Questions 19 and 20 .

The intestinal tract of a human foetus is sterile.
After birth, microflora from the mother are transferred to the baby's mouth through close contact. After a year, the microflora of the baby is similar to the mother's, with the baby's immune system ignoring these microbes.

Also during the first year of life, breast milk from the mother provides antibodies to the baby for any disease the mother has already experienced. When breastfeeding ceases, these antibody levels in the baby start to fall.

After the first year, any new species of invading bacteria is treated as a pathogen by the baby's immune system.

 

Question 19

A medical consequence for six-month-old babies that have only been bottle-fed with formula milk and not breastfed is that

  1. they will not develop microflora.
  2. their immune system will be damaged.
  3. their consumption of milk cannot be quantified.
  4. they will be at increased risk of infectious disease.

 
Question 20

Strict hygiene practices are followed in the care of newborns, whereas hygiene practices in the care of older babies are less emphasised.

Which of the following is the best reason for this difference?

  1. Vaccinations render personal hygiene unnecessary for older babies.
  2. Procaryotic cells are not identified as antigens in early development.
  3. Antibiotic treatments kill bacterial populations in the digestive system.
  4. Early exposure to pathogens helps to build a strong immune system.

 

Show Answers Only

Q19.  `D`

Q20.  `B`

Show Worked Solution

Q 19.

→ Bottle fed babies will not have the added immunity that is provided by the mother’s breast milk.

→ They will therefore have immune systems that are more susceptible to infectious disease.

`=>D`
  

Q20.

→ The immune systems of newborns will not work as efficiently as that of older babies as their immune systems are underdeveloped.

`=>B`


♦ Mean mark Q20 45%.