Question

A 50 g ball of clay is thrown horizontally at 10 m/s toward a 1.5 kg block sitting at rest on a frictionless surface. The clay hits and sticks to the block.

Part A

What is the speed of the block and clay right after the collision?

Express your answer using two significant figures.

Part B

What impulse does the clay exert on the block?

Express your answer using two significant figures.

Part C

What impulse does the block exert on the clay?

Express your answer using two significant figures.

Answer 1

let V be their joint speed after sticking
momentum conservation (despite inelastic collision)
m1 u1 + m2u2 = (m1+m2) V
0.050*10 + 0 = (1.5+0.050)V
V = 0.323 m/s
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impulse exerted by ball [ON block]
= change in momentum of block = m2[V-0] = 1.5*[0.323] = 0.485 N-s
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impulse exerted by block [ON ball]
= change in momentum of ball = m1[V-10] = 0.05[0.323 - 10] = -0.484 N-s
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they are same in magnitude, but opposite in direction
means >> gain in momentum of block = loss in momentum of ball