3C.1.1 Momentum and impulse Quiz: Pearson Edexcel Further Maths, Unit 25

The 20 questions

1. What is the momentum of a particle of mass m moving with velocity v?

   • m/v
   • (1/2) m v^2
   • mv
   • m v^2

2. What does the impulse-momentum principle state?

   • The impulse equals the work done on the body
   • The impulse equals the change in its kinetic energy
   • The impulse acting on a body equals the change in its momentum
   • The impulse equals its momentum divided by the time taken

3. What are the units of impulse?

   • J
   • N m
   • N s, equivalently kg m s^-1
   • kg m^2 s^-2

4. When is the momentum of a system conserved in a collision between two spheres?

   • Whenever friction acts on the spheres during impact
   • When no external impulsive forces act, so only the forces between the spheres act during impact
   • Only when the collision is perfectly elastic
   • When the total kinetic energy is conserved in every collision

5. Which of these is a scalar quantity?

   • Impulse
   • Kinetic energy
   • Momentum
   • Velocity

6. In which direction does an impulse act on a particle?

   • Opposite to the change in velocity
   • In the same direction as the change in velocity
   • Perpendicular to the change in velocity
   • In the same direction as the initial velocity

7. Two particles have equal momentum magnitudes. Must they have equal speeds?

   • Yes, because they must then have equal kinetic energy
   • Yes, if the particles are moving in the same direction
   • Not necessarily: speed is momentum divided by mass, so equal speeds need equal masses
   • Yes, because momentum depends only on speed

8. A ball of mass 0.2 kg moving at 5 m/s hits a wall and rebounds at 3 m/s. What is the magnitude of the impulse on the ball?

   • 8.0 N s
   • 1.6 N s
   • 0.4 N s
   • 1.0 N s

9. A ball rebounds from a wall as in the previous setting. In which direction does the impulse on the ball act?

   • Towards the wall, in the direction of the incoming ball
   • Zero, because the wall does no work on the ball
   • Away from the wall, opposite to its incoming direction
   • Parallel to the wall, along its surface

10. A sphere of mass 2 kg moving at 3 m/s collides with a stationary sphere of mass 1 kg and they coalesce. What is their common speed?

    • 2 m/s
    • 3 m/s
    • 1.5 m/s
    • 6 m/s

11. In the collision in the previous setting, how much kinetic energy is lost?

    • 6 J
    • 9 J
    • 3 J
    • 1.5 J

12. A particle of mass 4 kg moving at 2 m/s receives a constant force of 12 N in the direction of motion for 3 s. What is its final speed?

    • 20 m/s
    • 5 m/s
    • 9 m/s
    • 11 m/s

13. A ball of mass 0.5 kg hits the floor moving down at 6 m/s and rebounds upwards at 4 m/s. What is the impulse from the floor on the ball?

    • 5 N s downwards
    • 1 N s upwards
    • 3 N s upwards
    • 5 N s upwards

14. A bullet of mass 0.02 kg travelling at 300 m/s stops in 0.05 s. What is the average force on it?

    • 120 N
    • 300 N
    • 12 N
    • 6 N

15. A sphere of mass 3 kg moving at 4 m/s collides with a sphere of mass 1 kg moving at 2 m/s in the opposite direction, and they coalesce. What is their common velocity?

    • 2.5 m/s in the original direction of the 1 kg sphere
    • 1.0 m/s in the direction of the 3 kg sphere
    • 4.0 m/s in the original direction of the 3 kg sphere
    • 2.5 m/s in the original direction of the 3 kg sphere

16. A particle of mass 2 kg has velocity (3i + j) m/s and receives an impulse of (4i - 2j) N s. What is its velocity afterwards?

    • 7i - j m/s
    • 5i m/s
    • 3i + j m/s
    • 5i + 3j m/s

17. A particle of mass 2 kg has a force F = 4t N applied for 0 <= t <= 3 s, starting from rest. What is its speed at t = 3?

    • 4.5 m/s
    • 18 m/s
    • 36 m/s
    • 9 m/s

18. A tennis ball of mass 0.15 kg moving at -20 m/s is struck and leaves at 30 m/s over a contact time of 0.002 s. What is the average force on the ball?

    • 7500 N
    • 375 N
    • 1500 N
    • 3750 N

19. Why do airbags reduce injury in a crash?

    • They increase the time over which the momentum changes, which lowers the average force for the same impulse
    • They increase the momentum of the passenger
    • They reduce the change in momentum of the passenger
    • They make the impulse larger so that the passenger slows down more quickly

20. Two particles of masses 2 kg and 3 kg move with velocities 5 m/s and -1 m/s, and they stick together. What is the common velocity?

    • 0 m/s
    • 2.5 m/s in the positive direction
    • -1.4 m/s
    • 1.4 m/s in the positive direction

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