Question

Blocks $A$ and $B$ are resting on a smooth horizontal surface given equal speeds of $2ms^{- 1}$ in opposite sense as shown in the figure.

At $t=0$ the position of blocks are shown, then the co-ordinates of center of mass at $t=3s$ will be :-

• A. $\left(1 , 0\right)$
• B. $\left(3 , 0\right)$
• C. $\left(5 , 0\right)$
• D. $\left(2 . 25 , 0\right)$

Answer 1

Answer: (D)

$x_{cm_{f}}=x_{cm_{i}}+v_{c m}\times t$
Here $v_{c m}=\frac{4 \times 2 - 4 \times 2}{4 + 4}=0$
$x_{C M}=\frac{4 \times 0 + 4 \times 4 . 5}{4 + 4}=2.25m$
$y_{c m}=0$