Question

A lift whose cage is $3m$ high is moving up with an acceleration of $2m/s^2$. A piece of stone is dropped from the top of the cage of the lift when its velocity is $8m/s$. If $g=10m/s^2$, then the stone will reach the floor of the lift after.

• A. $0.7s$
• B. $0.5s$
• C. $0.4s$
• D. $0.3s$

Answer 1

The correct option is D $0.3s$

The time taken to reach the stone on the floor is given as,

$s=ut+\frac{1}{2}\left(a+g\right)t^2$

$3=8\times t+\frac{1}{2}\left(2+10\right)t^2$

$3=8\times t+6t^2$

$t=0.3052\sec$