A particle of mass moving at collides with a particle of mass at rest. They coalesce. Find their common speed.

Answer and explanation

Correct answer: A.

  1. Step 1: Momentum is conserved: .
  2. Step 2: , so m s.
Answer
.
Why not the others: is what you get if you ignore the second particle's mass. is what you get if you divide by the second mass only. is what you get if you add the speeds.

Practise more Applied Maths: Kinematics, Dynamics, Energy and Momentum.

Free questions with an explanation for every one, and full timed GCE Advanced Level (Sri Lanka) mock tests.