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Two bodies of masses 3kg and 5kg moving with velocities 2...

Two bodies of masses 3kg and 5kg moving with velocities 2 m/s and V m/s respectively in opposite directions collide. If they move together after collision with velocity 3.5 m/s in the direction of the 5kg mass, find the value of V.

A.

7.8 m/s

B.

6.8 m/s

C.

5.6 m/s

D.

4.6 m/s

Correct answer is B

Since the bodies are in an opposite direction, one takes the negative velocity.

m1v1+m2v2=(m1+m2)v (Momentum when the two bodies move in the same direction after collision)

3(2)+5(V)=(3+5)3.5

6+5V=285V=34;V=6.8m/s