A pebble is dropped freely in a well from its top. It takes the 20s for the pebble to reach the water surface in the well. Taking g = 10m/s2 and speed of sound =330m/s. find the time when the sound is heard after the pebble is dropped.
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Solution
Given:t=20s,g=10m/s2
Assume ‘h’ to be the depth of the well,
We know from the equation of motion,
H=ut+12gt2
=0+12(10)(20)2
=2000m
Finding the time when the sound is heard after the pebble is dropped––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––:
Given: speed of sound =330m/s
Timetaken=depthspeed
=2000330=6.1s
For the pebble to reach the water surface, it takes 20s,
Hence the total time taken when the sound is heard after the pebble is dropped