Examine the drawing shown. A bullet with a mass of 30 grams is fired from a high

Question

Examine the drawing shown. A bullet with a mass of 30 grams is fired from a high powered rifle. The bullet strikes a suspended wood block block, that has a recorded mass of 1.8 kg. When struck' the bullet becomes embedded within the wood block, causing the block and bullet to elevate to the position shown. Is the impact an example of an elastic, inelastic, or complete,ly inelastic collision? Explain your choice. At their highest point, what was the potential energy of the combined wood-bullet system.? What was the velocity of the combined wood-bullet system as it began to elevate through the arc shown? What was the velocity of the bullet prior to impact ? Within the gun, the bullet was initially at rest. Then when the gunpowder goes off, a Force causes the bullet to move forward through the barrel of the gun. Let us assume that the velocity of the bullet when it exited the barrel was the same as when it took off right after the gunpowder explosion. If the explosion lasted say, 0.01 seconds, then what Force value made the bullet move?

Explanation / Answer

A.

It is completely inelastic collision

B.

the potential energy is (M+m)gh

P.E = (1.8+0.03)*9.8 * 0.4

P.E = 7.17 J

C.

the velocity of combined system is

v = sqrt(2*g*h)

v = sqrt(2*9.8*0.4)

v = 2.8 m/s

D.

From conservation of momentum

m * v1 = (M+m)*v

v1 = (1.8+0.03)/0.03 * 2.8

v1 = 170.8 m/s

E.

impulse = change in momentum

F * t = m * v1

F = 512.4 N

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