Question

1.Two trolleys X and Y with momenta 20 Ns and 12 Ns respectively travel along a straight line in opposite directions before collision. After collision the directions of motion of both trolleys are reversed and the magnitude of the momentum of X is 2 Ns. What is the magnitude of the corresponding momentum of Y?

2.A force of 2i+7j N acts on a body of mass 5kg for 10 seconds. The body was initially moving with constant velocity of i−2j m/s. Find the final velocity of the body in m/s, in vector form.

Answer 1

1. Use conservation of momentum. Let the initial direction of X be considered positive.

20 - 12 = -2 + (momentum of Y)
Momentum of Y = 10 N*s

2. Momentum of Force*t = 20i + 70j (N*s)
is added to the body

Initial momentum = 5i -10j
Final momentum = 25i + 60 j
Divide than by the mass for the final velocity vector.
Final velocity = 5i + 12j m/s