Question

A force $F$ is applied on the upper pulley as shown in the figure. If $F=30t$, where $t$ is time in seconds, find the time when $m_1$ losses contact with floor. (Take $g=10m/s^2)$.

• A. $1sec$
• B. $1.66sec$
• C. $2sec$
• D. None of these

Answer 1

The correct option is C $2sec$

$\text{For}m\text{, to lose contact with floor:}$

$\text{(Normal)}N=0$

$\text{Equating,}$

$\text{2}T=40N$

$\Rightarrow T=20N$

$\text{given,}$

$F=\left(30t\right)N$

$\text{solving,}$

$F=3T$

$\Rightarrow 30t=3T$

$\Rightarrow 30t=3\times 20N$

$\therefore t=2s$