Question

In a police ballistics test, a 10.0-g bullet moving at 300 m/s is fired into a 1.00-kg block at rest. The bullet goes through the block almost instantaneously and emerges with 50.0% of its original speed. What is the speed of the block just after the bullet emerges

Answer 1

Speed of block after the bullet emerges = 1.5 m/s

Step-by-step explanation:

Here momentum is conserved.

Initial momentum = Final momentum.

Mass of bullet = 10 g = 0.01 kg

Initial Velocity of bullet = 300 m/s

Mass of block = 1 kg

Initial Velocity of block = 0 m/s

Final Velocity of bullet = 50% of initial velocity. = 150 m/s

We need to find final velocity of block. Let it be v

We have

Initial momentum = 0.01 x 300 + 1 x 0 = 3 kg m/s

Final momentum = 0.01 x 150 + 1 x v = 1.5 + v

Equating

3 = 1.5 + v

v = 1.5 m/s

Speed of block after the bullet emerges = 1.5 m/s