A-level · Momentum

Conservation of linear momentumExam-style questions

The principle that the total momentum of a system is unchanged by a direct collision — how to set it up with a consistent positive direction, the special case where the bodies coalesce (stick together) and move with a common velocity, and how to read the sign of the answer as a direction.

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19 questions · A Level level · mark scheme and worked solution on each · no sign-up to try

DifficultyAll Level 2 Level 3 Level 4 Level 5

1
Two particles $A$ (mass $0.6\text{ kg}$ ) and $B$ (mass $0.4\text{ kg}$ ) move towards each other on a smooth horizontal surface. $A$ moves at $5\text{ m s}^{-1}$ and $B$ moves at $2.5\text{ m s}^{-1}$ . They collide and coalesce.
(a) Find the speed and direction of the combined particle immediately after the collision. (3 marks)
(b) The combined particle is then brought to rest by a constant resistive force in $0.8\text{ s}$ . Find the deceleration of the particle and the distance it travels before coming to rest. (4 marks)
Level 4 · 7 marksTry it
2
Particle $P$ (mass $1\text{ kg}$ ) moves at $6\text{ m s}^{-1}$ towards a stationary particle $Q$ (mass $2\text{ kg}$ ). They collide and coalesce; the combined particle then collides with a stationary particle $R$ (mass $3\text{ kg}$ ) and all three coalesce.
(a) Find the speed of the combined particle after the first collision. (3 marks)
(b) Find the final speed after the second collision. (3 marks)
Level 4 · 6 marksTry it
3
A gun of mass $4\text{ kg}$ , initially at rest and free to move, fires a bullet of mass $0.02\text{ kg}$ horizontally at $300\text{ m s}^{-1}$ .
(a) Find the recoil speed of the gun. (3 marks)
(b) Explain why the total momentum of the system is zero after firing. (1 mark)
Level 4 · 4 marksTry it