Question

A stone is dropped into a lake from a tower $500$ metre high. The sound of splash will be heard by the man approximately after:

• A. $11.5sec$
• B. $21sec$
• C. $10sec$
• D. $14sec$

Answer 1

The correct option is A $11.5sec$

Time taken by stone
$t=\sqrt{\frac{2s}{g}}$
$\therefore t=\sqrt{\frac{2\times 500}{10}}$
$\Rightarrow t=\sqrt{\frac{1000}{10}}=\sqrt{100}$
$\Rightarrow t=10s$
Time taken by sound $=\frac{500}{332}\approx 1.5s$
$\therefore$ Total time $=10+1.5=11.5s$