Question

A splash is heard 3.12s after a stone is dropped into a well 45m deep.the speed of sound in air is(g=10m/s2)

Answer 1

Let the speed of sound be s. Then the time taken for the splash to be heard is 45/s seconds.

That means that the stone fell for 3.12 - 45/s seconds.

You know that stone fell 45m, so

5(3.12-45/s)^2 = 45
s = 375 m/s

not too close to the expected value of 343 m/s...

Answer 2

The time when the stone reaches the ground =(45*2)/10=3 sec.so,time taken by sound = 3.12-3= 0.12 sec. Now distance travelled by sound is 45 m,time=0.12sec . Speed=distance/ time =45/0.12=375m/sec