Question

A stone is dropped down a deep well from rest. The well is 50metre deep. How long will it take to reach the bottom of the well. Given a=9.8m/s

Answer 1

Given  that,

a  =  9.8 m/s2

u  =  0

s  =  50m


By  Newton's  law  of  motion,

v2  -  u2  =  2as,

ie,  v2  -  [0]2  =  2 * 9.8 * 50

ie,  v2  =  980.

So,  v  =  Root  of  980

=  31.304.....


Now,  we  got  the  final  velocity  v.

So,  we  can  find  the  time  required,  by  Newton's  equation  of motion,

v  =  u  +  at.

ie,  31.304  =  0  +  9.8 * t

31.304  =  9.8t

So,  t  =  31.304  /  9.8

ie,  31.30 * 100  /  9.8 * 100

=  3130  /  980

=  3.193.......m / s.