A 60 kg swimmer suddenly dives from a 150 kg raft with a speed of 1.5 m/s. The raft is initially at rest. What is the speed of the raft immediately after the diver jumps if the water has negligible
effect on the raft?

v2 = 0.6 m/s in opposite direction

Explanation:

The computation of the speed of the raft is as follows

The center of system mass would be remains at the same place also it has no external force applied

Therefore

V = 0

So,  

M1.V1= - (M2.V2)

where,

M1 = 60 kg, V1 = 1.5 m/s

M2 = 150 kg

Now  

60 × 1.5 = - 150 × v2

v2 = -0.6 m/s

v2 = 0.6 m/s in opposite direction

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