Block A in (Figure 1) has mass 1.15 kg , and block B has mass 3.05 kg . The bloc

Question

Block A in (Figure 1) has mass 1.15 kg , and block B has mass 3.05 kg . The blocks are forced together, compressing a spring S between them; then the system is released from rest on a level, frictionless surface. The spring, which has negligible mass, is not fastened to either block and drops to the surface after it has expanded. Block B acquires a speed of 1.45 m/s .

Part A What is the final speed of block A? Express your answer in meters per second to three significant figures.

Part B How much potential energy was stored in the compressed spring?

Explanation / Answer

initial moemtum Pi = mA*uA + mB*uB = 0

final moemtum

Pf = mA*vA - mB*vB

given vB = 1.45 m/s

(mA*vA) = mB*vB

1.15*vA = 3.05*1.45

vA = 3.85 m/s

++++++++++++++++++

PE = KEA + KEB = 0.5*mA*vA^2 + 0.5*mB*vB^2

PE = (0.5*1.15*3.85^2)+(0.5*3.05*1.45^2) = 11.73 J <<----------answer

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