Question

A body is dropped from a height of 100 m. Find out the time interval in which it will reach ground. Also find the velocity with which it will hit ground.
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Answer 1

$Given :-$

A body is dropped from a height of 100 m. Find out the time interval in which it will reach ground. Also find the velocity with which it will hit ground.

$Solution :-$

h= 100 m is given.

At the time of striking the ground , the velocity ,

vg=sqrt(2gh)=sqrt(2*10*100)= sqrt(2000)………………..(1)

We have taken g=10 m/s^2.

When the body falls through ,say h1, it's velocity will be

v1=sqrt(2*g*h1)

Squaring on both sides,

v1^2=2*g*h1 or

h1= v1^2/2g.

So, height from the ground=h-h1=100-(v1^2/2g)…….(2)

But, v1= vg/2 or

v1^2=vg^2/4=2000/4=500 m/s

Using this value in (2),

Height from the ground=100–500/20=75m.