Question

An iron block is dropped into a deep well.Sound of splash is heard after 4.23 s.If the depth of the well is 78.4 m, then find the speed of sound in air $\left(g=9.8m/s^2\right)$

• A. 338 m/s
• B. 320 m/s
• C. 280 m/s
• D. 340.8 m/s

Answer 1

The correct option is A 338 m/s

Assuming no air (or air drag) on stone, the time it takes stone to reach water is:

t = √2h/g = √2(78.4)/9.81 = √15.98369 = 3.998 s

time for sound to travel 78.4 m = 4.23 - 3.998 = 0.232 s

speed of sound in well = 78.4/0.232 = 338 m/s