Question

A man is raising himself and the crate on which he stands with an acceleration of $5m{s}^{-2}$ by a massless rope-and-pulley arrangement. Mass of the man is $100kg$. If $g=10m{s}^{-2}$,, the contact force between the man and the crate is:

• A. $2250N$
• B. $1125N$
• C. $750N$
• D. $375N$

Answer 1

The correct option is D $375N$

$\left(D\right)$

When the man applies a force of $T$, the string creates equal force $T$ as tension. The same tension $T$ acts on the crate too.

$\therefore$ Total force acting on the system will become $2T$.

$\Rightarrow 2T-150g=150\times 5$

$\Rightarrow T=1125N$

$\therefore$ The man applies a force of $1125$ $N$ on the rope.

The constant force between the man and the crate is given by,

constant force, $F=$ Weight of man $+$ crate $-$ force applied by man.

$=150g-1125$

$=1500-1125$

$=375N$.