Question

A pebble is dropped freely in a well from its top . It takes 20 seconds for the pebble to reach the after surface in the well . Taking gravity as 10 m/s^2 and speed of sound =330m/s , find the depth of after surface and the time when echo is heard after the pebble is dropped

Answer 1

Answer:

Explanation:

the pebble is freely dropped, so its initial speed will be 0

i.e, u=0

time taken is 20 s, therefore t=20s

acceleration due to gravity is 10m/s^2, therefore a=10m/s^2

we know that,

S=ut+1/2 at^2, but u=0

so s=1/2at^2

s=1/2 x 10 x 20 x 20= 2000m

Therefore , the depht of the well is 2000m, (which is ridiculous)

and the time taken for the sound of the pebble dropping will be

t=d/s

t=2000/330= 6.06s

hope it helps and have a nice day!