MOMENTUM
4 marks · NormalA trolley of mass 2 kg is moving at 3 m/s towards a stationary trolley of mass 1 kg. They collide and stick together.
Calculate the total momentum before the collision.
Calculate the velocity of the joined trolleys after the collision.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
Show answer
(a) 6 kg m/s
(b) 2 m/s
Common mistakes: Not combining masses after collision
Show mark scheme and worked solution
Marking points
M1 (a) · 1 mark · Calculates momentum of moving trolley (2 × 3).
A1 (a) · 1 mark · Gives 6 kg m/s with unit.
M2 (b) · 1 mark · Uses conservation of momentum and combines masses for after collision. (follow-through)
A2 (b) · 1 mark · Gives final velocity as 2 m/s, correct unit. (follow-through)
Worked solution
a) Only one trolley moves, so p = 2 × 3 = 6 kg m/s
b) Both trolleys together after collision: total mass = 2 + 1 = 3 kg