Question

In the given arrangement, strings and pulleys are light and all surface are frictionless and take $g=10{\text{m/s}}^2$. Assuming at $t=0$, system is released from rest, find the speed of block $A$ (in decameter/sec) at $t=2\text{sec}$.

Answer 1

The system can be redrawn as


Acceleration $a=\frac{\text{Force}}{\text{Total mass}}$
$\therefore a=\frac{4mg}{8m}=\frac{g}{2}=5{\text{m/s}}^2$
$\{\because g=10{\text{m/s}}^2\}$
From first equation of motion
$\because v=u+at=2\times 5=10\text{m/s}$