Momentum Practice Questions

Which of these is the correct unit of momentum?

Put a cross ( ☒ ) in the box next to your answer.

☐ A $\mathrm{kg\ m/s^2}$

☐ B $\mathrm{kg/m/s}$

☐ C $\mathrm{kg\ m/s}$

☐ D $\mathrm{kg/m/s^2}$

A football has a mass of $440\ \mathrm{g}$.

The football is kicked and moves off at a velocity of $18\ \mathrm{m/s}$.

Calculate the momentum of the football.

momentum = .............................................................. $\mathrm{kg\ m/s}$

State what is meant by the inertial mass of an object.

A resultant force of $48\ \mathrm{N}$ acting on the toy car produces an acceleration of $6.0\ \mathrm{m/s^2}$.

Calculate the inertial mass of the toy car.

inertial mass = .............................................................. $\mathrm{kg}$

Calculate the total momentum of the two dodgem cars before the collision.

total momentum = .............................................................. $\mathrm{kg\ m/s}$

Calculate the velocity of the two dodgem cars immediately after the collision.

velocity = .............................................................. $\mathrm{m/s}$

The total kinetic energy of the dodgem cars after the collision is less than the total kinetic energy before the collision.

Explain why the total momentum is still the same before and after the collision.

Calculate the change in momentum of the tennis ball.

change in momentum = .............................................................. $\mathrm{kg\ m/s}$

The racket is in contact with the ball for $25\ \mathrm{ms}$.

Calculate the average force exerted on the ball by the racket.

Use an equation selected from the list of equations at the end of this paper.

average force = .............................................................. $\mathrm{N}$

Show that the total momentum of the two trolleys before the collision is $0.80\ \mathrm{kg\ m/s}$ to the right.

After the collision, trolley A moves to the left at $0.50\ \mathrm{m/s}$.

Calculate the velocity of trolley B after the collision.

State the direction of its velocity.

velocity of B = .............................................................. $\mathrm{m/s}$

direction ..............................................................

State the total momentum of the student and the ball before the ball is thrown.

Calculate the speed of the student immediately after she throws the ball.

speed of the student = .............................................................. $\mathrm{m/s}$

A student is given two trolleys, A and B, which stick together when they collide. The trolleys run on a level track. The student also has a top-pan balance, a card of known length that can be fixed to a trolley, and two light gates connected to a computer that records the time for which each light gate is blocked.

Trolley A is given a push so that it runs along the track and collides with trolley B, which is stationary between the two light gates.

Explain how the student could use this equipment to test whether momentum is conserved in the collision.

Your explanation should include:

• the measurements the student should take
• how the results should be used
• precautions needed to obtain accurate results.

Calculate the magnitude of the change in momentum of the ball.

change in momentum = .............................................................. $\mathrm{kg\ m/s}$

The ball is in contact with the wall for $0.040\ \mathrm{s}$.

Calculate the magnitude of the average force exerted by the wall on the ball.

Use an equation selected from the list of equations at the end of this paper.

average force = .............................................................. $\mathrm{N}$

The same ball is now thrown at the same speed at a thick foam mat fixed to the wall. It rebounds at the same speed as before, but the contact time is longer.

Explain the effect of the foam mat on the average force exerted on the ball.

Calculate the velocity of the trolley at the end of the $4.0\ \mathrm{m}$.

Use an equation selected from the list of equations at the end of this paper.

velocity = .............................................................. $\mathrm{m/s}$

At the end of the $4.0\ \mathrm{m}$ the trolley collides with a stationary trolley of mass $0.20\ \mathrm{kg}$.

The two trolleys stick together.

Calculate the velocity of the trolleys immediately after the collision.

velocity = .............................................................. $\mathrm{m/s}$