Question

Blocks A and B are resting on a smooth horizontal surface given equal speeds of $2\text{m/s}$ in opposite sense as shown in the figure.

At $t=0$, the position of blocks are shown, then the co-ordinates of centre of mass at $t=3\text{s}$ will be

• A. $(1,0)$
• B. $(3,0)$
• C. $(5,0)$
• D. $(2.25,0)$

Answer 1

The correct option is D $(2.25,0)$

At $t=0$ centre of mass is at mid-point or at $(2.25,0)$
Velocity of centre of mass is zero.
Hence centre of mass will remain at this position all the time.