Question

Two blocks of mass $m=5kg$ and $M=10kg$ are connected by a string passing over a pulley $B$ as shown. Another string connects the centre of pulley $B$ to the floor and passes over another pulley $A$ as shown. An upward force $F$ is applied at the centre of pulley $A$. Both the pulleys are mass-less. An upward force $F$ is applied in the pulley $A$. Find the acceleration of blocks $m$ and $M$, if $F$ is $100N$.

• A. $0m/s^2;0m/s^2$
• B. $5m/s^2;2.5m/s^2$
• C. $10m/s^2;5m/s^2$
• D. $2.5m/s^2;5m/s^2$

Answer 1

Answer: (A)

$0m/s^2;0m/s^2$

Let $T_0=$ tension in the string passing over A
and $T=$ tension in the string passing over B
$\therefore 2T_0=F$ and $2T=T_0$
$\Rightarrow T=F/4=25N$

$T=F/4=25N$
Weights of blocks are

$mg=50N$

and $Mg=100N$
As $T<mg$ and $Mg$ both, the blocks will remain stationary on the floor.