Question

A well is 19.6 m deep, a atone is dropped in it. After 2.06 s, echo sound is heard, then the velocity of sound is

• A. 326.7 m/s
• B. 380 m/s
• C. 300.8 m/s
• D. 342.3 m/s

Answer 1

Answer: (A)

326.7 m/s

From the equation of motion
$h-ut+\frac{1}{2}g{t}^2$
$u=0,t=\sqrt{\frac{2h}{g}}+\frac{h}{v}$ [For echo]
Given, $h=19.6m,g=9.8m/s^2,t=2.06$
$\Rightarrow t=\sqrt{2\times \frac{19.6}{9.8}}+\frac{19.6}{u}=2.06$
$\Rightarrow v=326.7m/s$