Physics-Momentum

Question

A 0.010 kg bullet is fired at a 0.50 kg block initially at rest. The bullet, moving with an initial speed of 100.0 m/s emerges from the block with a speed of 75 m/s. What is the speed of the block after the collision?

Answer 1

This can be solved by using the concept of conservation of momentum. The total momentum of the system should be conserved, before collision and after collision.

Lets assume:

u1: initial velocity of the bullet

v1: final velocity of the bullet

u2: initial velocity of the block (it is 0 as it is in rest)

v2: final velocity of the block

By using the conservation:

m1u1 + m2u2 = m1v1+m2v2

remember: u2 = 0 (the block is in rest)

solving this will give:

v2 = m1(u1-v1)/m2

gives v2 = 0.5 m/Sec