Question

A stone is dropped into a lake from a tower 500m high. The sound of the splash will be heard by a man on the tower after a time of (velocity of sound in air=350 m/s)

• A. $21s$
• B. $10s$
• C. $11.4s$
• D. $1s$

Answer 1

The correct option is C $11.4s$

$t=$ time for stone to reach from A to B,

$t=\sqrt{\frac{2H}{g}}=\sqrt{\frac{2\times 500}{10}}=10sec$,

$t_1=$ time for sound to reach from B to A,

$\Rightarrow t_1=\frac{500}{350}=\frac{10}{7}=1.4sec$

So, total time $=t+t_1=10+1.4=11.4sec$.