[2](a)A tennis ball of mass 58 g is served at 45 m/s. Calculate its momentum.

[3](a)A 2.0 kg trolley moving at 3.0 m/s collides with a stationary 1.0 kg trolley, and they stick together. Calculate their common velocity after the collision.

[1](b)State the law of conservation of momentum used in part (a).

[3](a)A ball of mass 0.16 kg hits a wall at 8.0 m/s and rebounds at 6.0 m/s in the opposite direction. Calculate the change in momentum of the ball.

[2](b)The collision with the wall lasts 0.05 s. Calculate the average force exerted on the ball by the wall.

[3](a)Two skaters, initially at rest, push off from each other. Explain, using momentum, why they move off in opposite directions.

[2](a)A car of mass 1200 kg travels at 20 m/s. Calculate its momentum.

[3](a)A force acts on a 900 kg object, increasing its velocity from 0 to 15 m/s in 3 s. Calculate the average force, using the impulse-momentum relationship.

[3](a)A 3 kg trolley moving at 4 m/s collides and joins with a 2 kg trolley moving at 1 m/s in the opposite direction. Calculate their common velocity afterwards, taking the 3 kg trolley's direction as positive.

[2](a)A 50 kg astronaut at rest in space throws a 0.5 kg tool away at 100 m/s. Calculate the astronaut's recoil velocity.

[2](a)State the law of conservation of momentum.

[2](a)Explain, in terms of momentum, why a boxer's glove is padded, considering the effect on the force experienced by the person hit.