Question

A lift is moving with uniform downward acceleration of 2 $m/s^2$. A ball is dropped from a height 2 m from the floor of lift. Find the time after which ball will strike the floor

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

Answer 1

Answer: (A)

$\frac{1}{\sqrt{2}}sec$

In the frame of lift the downward acceleration of the ball will be $a=g-2=10-2=8m/s^2$

so the time taken will be given by $h=\frac{1}{2}a{t}^2$ or $t=\sqrt{\frac{2h}{a}}=\frac{1}{\sqrt{2}}sec$