Figure shows two blocks of masses `5 kg` and `2 kg` placed on a frictionless surface and connected with a spring. An external kick gives a velocity of `14 m//s` to the heavier block in the direction of lighter one. Deduce (a) velocity gained by the centre of mass and (b) the separate velocities of the two blocks in the centre of mass coordinates just after the kick.

Options

A. `4 m//s, 4 m//s`
B. `10 m//s, 4 m//s`
C. `4 m//s, 10 m//s`
D. `10 m//s, 10 m//s`

Answer

C

Explanation

( c) `v_(cm)=(m_1 v_1 + m_2 v_2)/(m_1 + m_2) =(2 xx 0+ 5 xx 14)/(2 + 5) = 10 m//s`
`v_1 = V_(cm) = 14 - 10 = 4 m//s`
`v_2 = V_(cm) = 0 - 10 = - 10 m//s`.
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