Question

A stone of mass 5 kg falls from the top of a 50 m high building and penetrates 1 m deep in the sand. Find the time taken to penetrate.

• A. $\frac{\sqrt{5}}{50}s$
• B. $\frac{\sqrt{10}}{50}s$
• C. $\frac{\sqrt{5}}{10}s$
• D. $\frac{\sqrt{10}}{10}s$

Answer 1

The correct option is B $\frac{\sqrt{10}}{50}s$

Velocity on striking the sand,
$u=\sqrt{2gh}=\sqrt{2\times 10\times 50}=\sqrt{1000}m/sFrom,v^2-u^2=2as0-1000=2\times a\times 1a=-500m/s^{2}From,v=u+at0=\sqrt{1000}-500tt=\frac{\sqrt{1000}}{500}=\frac{\sqrt{10}}{50}s$