A stone is dropped in a well of depth 500 m and a sound is heard after 45/4 seconds. Then speed of sound is (if g= 10 m/s): x* 100 m/s. Find the value of x.
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Solution
Time taken by the stone to reach the water surface can be calculated using the equation of motion s = ut + ½ gt2 Here u = 0, s = 500 m , g = 10 m/s2
So t = (2x500/10)½ = 10 s
Therefore time taken by sound to travel this distance = 45/4 - 10= 11.25-10=1.25s Speed of sound in air = distance covered/Time = 500/1.25 = 400 m/s