Question

Two blocks A and B with mass $4kg$ and $6kg$ respectively are connected by a stretched spring of negligible mass as in figure. When the two blocks are released simultaneously the initial acceleration of B is $1.5m/s^2$ westward. The acceleration of A is then

• A. $1m/s^2$ westward
• B. $2.25m/s^2$ eastward
• C. $1m/s^2$ eastward
• D. $2.75m/s^2$ westward

Answer 1

The correct option is B $2.25m/s^2$ eastward

No any external force is acting on the system.

Therefore acceleration of center of mass will be zero.

$a_{com}=\frac{m_A{a}_A+m_B{a}_B}{m_A+m_B}$

$0=\frac{4a_A+6\times 1.5}{4+6}$

$a_A=-\frac{g}{4}=-2.25m/s^2$

Negative sign indicate acceleration of block A is opposite to block B.

Hence, $a_A=2.25m/s^2$ eastward.