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PHYSICS, M2 EQ-Bank 14 MC

A bowling ball, a golf ball, and a table-tennis ball are dropped simultaneously from a height of 2.0 m in a vacuum chamber. Which ball would you expect to reach the ground first?

  1. The bowling ball
  2. The golf ball
  3. The table-tennis ball
  4. All three balls would reach the ground at exactly the same time
Show Answers Only

\(D\)

Show Worked Solution
  • In the absence of air resistance, the only force acting on each ball is the gravitational force.
  • The acceleration of an object due to gravity is independent of its mass.
  • All three balls would fall with the same acceleration of 9.8 ms\(^{-2}\).

\(\Rightarrow D\)

PHYSICS, M2 EQ-Bank 5

Liam is carrying two boxes stacked on top of each other to a customer. The lighter 2.8 kg box is placed on top of the heavier 4.2 kg box.

Liam lifts the stack by applying an upward force of 40 N with each hand to the bottom of the heavier box, as shown below.
 

  1. Calculate the magnitude of the acceleration of the boxes as Liam lifts them.   (2 marks)
  1. Explain why the force that the 4.2 kg box applies to the 2.8 kg box is greater while the boxes are being accelerated than when they are stationary.   (2 marks)
Show Answers Only

a.    \(1.63\ \text{ms}^{-2}\)

b.    When the boxes are at rest:

  • The force that the 4.2 kg box applies to the 2.8 kg box is equal and opposite weight force of the 2.8 kg box.

When the boxes are accelerating:

  • The net force of the system is positive as the system is accelerating.
  • The 4.2 kg box must be applying extra force to the 2.8 kg box to cause it to accelerate at 1.63 ms\(^{-2}\).
Show Worked Solution
a.     \(F_{\text{net}}\) \(=\) total applied force upwards \(-\) weight force of the two boxes
    \(= (2 \times 40)-(7 \times 9.8)\)
    \(=11.4\ \text{N}\)

 
\(a=\dfrac{F_{\text{net}}}{m}=\dfrac{11.4}{7.0}=1.63\ \text{ms}^{-2}\)
  

b.    When the boxes are at rest:

  • The force that the 4.2 kg box applies to the 2.8 kg box is equal and opposite weight force of the 2.8 kg box.

When the boxes are accelerating:

  • The net force of the system is positive as the system is accelerating.
  • The 4.2 kg box must be applying extra force to the 2.8 kg box to cause it to accelerate at 1.63 ms\(^{-2}\).

PHYSICS, M2 EQ-Bank 3

A horizontal Atwood machine begins accelerating from rest along a horizontal track of length, \(L=4.00\ \text{m}\).

A block with a mass of 500 g takes 2.7 seconds to travel the full length of the track. A constant frictional force acts on the block, described by the equation \(F_f = \mu_k mg\)
  

  1. Determine the coefficient of kinetic friction between the 500 g block and the track.   (4 marks)
  1. Find the kinetic energy of the 500 g block when it reaches the end of the track.   (2 marks)
Show Answers Only

a.    \(0.154\)

b.    \(2.194\ \text{J}\)

Show Worked Solution

a.     Find system acceleration using  \(s=ut + \dfrac{1}{2}at^2\):

\(s\) \(=ut +\dfrac{1}{2}at^2\)  
\(4.00\) \(=0 + \dfrac{1}{2} \times a \times 2.7^2\)  
\(a\) \(=\dfrac{2 \times 4.00}{2.7^2}=1.097\ \text{ms}^{-2}\)  

 
\(\therefore\) Total system mass \((m_T)\) = 500 + 150=650\ \text{g} = 0.65\ \text{kg} \)
 

Find frictional force acting on the block:

\(F_{\text{net}}\) \(=F_{\text{applied}}-F_f\)  
\(0.65 \times 1.097\) \(= 0.15 \times 9.8-F_f\)  
\(F_f\) \(=1.47-0.713=0.757\ \text{N}\)  

 
\(\therefore \mu_k = \dfrac{F_f}{mg} = \dfrac{0.757}{9.8 \times 0.5} = 0.154\)
  

b.    Using  \(v^2=u^2 +2as:\)

\(v^2=u^2+2as = 0^2+2 \times 1.097 \times 4.00 = 8.776\ \text{ms}^{-1}\)

\(KE = \dfrac{1}{2}mv^2 = \dfrac{1}{2} \times 0.5 \times 8.776 = 2.194\ \text{J}\)

PHYSICS, M2 2023 VCE 8 MC

At a swimming pool, Sharukh and Sam, shown below, step off the low diving board at the same time. Over the small distance they fall, air resistance may be ignored. Sharukh and Sam have masses of 80 kg and 60 kg respectively.
 

Which one of the following best explains what happens to Sharukh and Sam as they drop straight down into the water?

  1. Sharukh reaches the surface first because she has a larger mass.
  2. The net force on Sharukh is larger than that on Sam, so Sharukh reaches the surface first.
  3. They both reach the surface together because they both experience the same downward force.
  4. They both reach the surface together because they both experience the same downward acceleration.
Show Answers Only

\(D\)

Show Worked Solution
  • Both Sharukh and Sam fall under the acceleration of gravity which is 9.8 ms\(^{-2}\).
  • They will fall at the same speed and therefore hit the surface at the same time.

\(\Rightarrow D\)

PHYSICS, M2 2014 HSC 3 MC

A pendulum is used to determine the value of acceleration due to gravity. The length of the pendulum is varied, and the time taken for the same number of oscillations is recorded.

Which of the following could increase the reliability of the results?

  1. Changing the mass of the pendulum
  2. Identifying the independent and dependent variables
  3. Recording all measurements to at least four significant figures
  4. Repeating each measurement several times and recording the average
Show Only

\(D\)

Show Worked Solution
  • Reliability of data can be increased by repeating the same experiment numerous times and recording an average from the data as it eliminates random error.

\(\Rightarrow D\)

PHYSICS, M2 2018 HSC 14 MC

A pendulum can be used to determine the acceleration due to gravity using the relationship

\(\displaystyle T=2 \pi \sqrt{\dfrac{l}{g}}\)

where \(T\) is the period and \(l\) is the length of the pendulum.

The acceleration due to gravity on the surface of Mars is less than that on Earth.

Which graph relates the variables for the pendulum correctly for both planets?
 

 
 

Show Answers Only

\(C\)

Show Worked Solution

  • Rearranging the equation given  \(\Rightarrow\ \ l=\dfrac{T^2}{4\pi^2} \times g\)
  • Thus \(\ l \propto T^2\).
  • It will be a nonlinear graph between \(l\) and \(T\).
  • As the value of \(g\) for Mars is less than that of Earth, the data line for Mars must be below that of Earth.
\(\Rightarrow C\)
♦ Mean mark 478%.

PHYSICS, M5 2018 HSC 11 MC

During the launch of a space vehicle from Earth, an astronaut feels an increased downward `g` force.

In which of the following situations would a person also feel an increased downward `g` force?
 

 

Show Answers Only

`D`

Show Worked Solution
  • A feeling of increased downwards `g` force is a result of upwards acceleration.
  • Options A, B and C all involve zero or downwards acceleration.

`=>D`