A ball of mass `1 kg` is thrown up with an initial speed of `4 m//s`. A second ball of mass `2 kg` is released from rest from some height as shown in Fig. Choose the correct statement (s).

Options

A. The centre of mass of two balls comes down with acceleration `gsqrt(3)`.
B. The centre of mass first moves up then comes down.
C. Acceleration of centre of mass is `g` downwards
D. The centre of mass comes down with constant velocity.

Answer

B, C

Explanation

Initially `v_(cm)` is upward. Hence centre of mass will move upward intially.
`a_(cm) = (1 xx g + 2 xx g)/(1 + 2) = g`