A stone is dropped from the top of a tower 500 m high into a pond of water at the base of the tower. When is the splash heard at the top ? Given, `g = 10ms^-2` and speed of sound = `340 ms^-1`.

Explanation

Distance covered by stone (s) =500m
Initial velocity `u= 0 ms^(-1)`
Acceleration due to gravity, `g= 10 ms^(-2)`
`S= u t + (1)/(2) g t^(2)`
`rArr 500 = 0+ (1)/(2) xx 10 xx t^(2)`
`rArr 500= 5t^(2)`
`rArr t^(2)=100 or t=10s`
Thus in 10 s the stone reaches the pond. Speed of sound `=340 ms^(-1)`
`therefore` Time taken by sound to cover
`500m= (500)/(340) =1.47 =1.5s`
`therefore` Total time taken `=(10+1.5)s`
=11.5s
In 11.5s the splash will be heard on top.