Question

Two blocks of masses $2kg$ and $5kg$ are at rest on the ground. The masses are connected by a string passing over a frictionless pulley which is under the influence of a constant upward force $F=50N$. The acceleration of $5kg$ and $2kg$ masses are

• A. $0,2.5m{s}^{-2}$
• B. $0,0$
• C. $2.5m{s}^{-2},2.5m{s}^{-2}$
• D. $1m{s}^{-2},2.5m{s}^{-2}$

Answer 1

The correct option is A $0,2.5m{s}^{-2}$

FBD of Individual bodies
$\Rightarrow 2T=50N$
$T=25N$
Total force downward due to $2kg$ is $20N$ as $T>20N,2kg$ mass will leave the ground
$F_{net}T-20=2a$
$\Rightarrow a=2.5m/s^2$
Total force downward due to $5kg$ is $50N$ as $T<505kg$ mass will be at rest on ground
$a_5=0$