A bullet of mass 0.016 kg and initial speed 540 m/s penetrates an initially stat

Question

A bullet of mass 0.016 kg and initial speed 540 m/s penetrates an initially stationary wooden block with a of mass 0.56 kg and lodges in it.

1. What is the initial velocity of the center of mass of the bullet-block system before the collision?

2. What is the velocity of the block (with the embedded bullet) after the collision?

3. How much mechanical energy was lost during the collision? (This mechanical energy was transformed into sound and friction generated heat.)

4. Now lets say that instead of being embedded in the block, the bullet comes out the other side of the block with a velocity of 363 m/sec. Assuming the block remains intact, what is its velocity after the collision?

Explanation / Answer

velocity of centre of mass = Summation [mv] / summation m

= 0.016 x 540 / 0.016 + .56

= 15 m/s

conserving initial and final momentum

m1v1 = [m1+m2 ]x v

= 0.016 x 540 / 0.016 + .56

v = 15 m/s

initital KE = 2332.8J

final KE = 64.8J

loss = 2268J

change in momentum of the bllet = 0.016 x [540 - 363] = 2.832 kgm/s

this momentun is gained by block

.56 x v = 2.832

v = 5.057m/s

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