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: Option B
Explanation
Since the bodies are in an opposite direction, one takes the negative velocity.
(m_{1}v_{1} + m_{2}v_{2} = (m_{1} + m_{2})v) (Momentum when the two bodies move in the same direction after collision)
(3(-2) + 5(V) = (3 + 5)3.5)
(-6 + 5V = 28 implies 5V = 34; V = 6.8 m/s)