Question

An elevator car whose floor to ceiling distance is equal to 2 m starts ascending with constant acceleration 2 $m/s^2$. $5sec$ after the start, a bolt begins falling from ceiling of car. Time after which bolt hits floor of elevator starting from fall. $(g=10m/s^2)$

• A. $0.7$ s
• B. $\frac{1}{\sqrt{2}}$ s
• C. $1.73$ s
• D. $\frac{1}{\sqrt{3}}$ s

Answer 1

The correct option is D $\frac{1}{\sqrt{3}}$ s


By placing the frame of reference on the lift, the kinematic parameters of the bolt becomes,
$u=0m/s,a=12m/s^2,s=2m$
$s=ut+\frac{1}{2}a{t}^2$
$\Rightarrow 2=\frac{1}{2}\times 12\times t^2\Rightarrow t=\frac{1}{\sqrt{3}}sec$