Question

If block B moves downward with an acceleration of $3m/s^2,$ find the acceleration of block A.

Answer 1

Pulley 2 is fixed. So we have,
acceleration of the string $=a_B=3m/s^2$

For pulley 1, we have one end fixed
$a_1=\frac{a+0}{2}=3$
($\because a_1=$ acceleration of the string connecting pulley 1 & 2 $=3m/s^2$)

$\therefore$ Acceleration of block A
$=a=6m/s^2$