Forces & Momentum (Edexcel A Level Physics): Structured Questions

A student carried out an experiment with coins.

She gave a 2p coin a sharp tap, so that it slid along a horizontal surface and came to rest as shown. 

The student recorded the distance s moved by the coin.

She then replaced the 2p coin with a 1p coin and repeated the process.

The student read that the frictional force between an object and a surface is directly proportional to the mass of the object. She suggested that, in her experiment, u is directly proportional to √s and is independent of the mass of the coin.

Discuss the validity of this suggestion.  

She arranged a collision between a 2p coin and a stationary 1p coin. She noted the directions in which the coins moved after the collision and determined their velocities.  

i) Show that the velocity of the 2p coin just before the collision was about 2 ms^-1 .

mass of 2p coin = 7.1 g

mass of 1p coin = 3.6 g 

(4)

ii) Show that the collision was inelastic

(2)

A student determines the acceleration of free fall g using a trolley on a ramp.

The trolley is released from rest and moves down the ramp. A card attached to the trolley interrupts a light gate near the bottom of the ramp, as shown.

The student varies the distance $s$ between the release position and the light gate. For each value of $s$, the student determines the velocity $v$ of the trolley as it passes through the light gate.

Describe the measurements that need to be made using this apparatus and how they are used to determine $v$ and $s$.

Explain why a graph of $v^2$ against $s$ gives a straight line through the origin.

The student plotted a graph of $v^2$ against $s$, as shown.

The ramp is inclined at an angle of 4.0° to the horizontal.

Determine a value for g using the graph.

The student's value for g is less than 9.81 m s^-2.

Give a reason for this difference.

The diagram shows two freight wagons, A and B, on a straight, horizontal railway track.

Wagon A moves towards wagon B. Wagon B is stationary. Wagon A collides with wagon B, and the wagons join together.

State the principle of conservation of momentum.

Explain how Newton's second and third laws show that the momentum of the wagons is conserved during the collision.

Before the collision, wagon A moved with a velocity of $3.0{\text{m s}}^{-1}$.

An operator claims that, after the collision, the wagons move at more than half the original speed of wagon A.

Assess whether this claim is correct.

mass of wagon A $=8000\text{kg}$

mass of wagon B $=16000\text{kg}$