Friday, January 8, 2016

A body is released from a height of 100 m falls freely. What is the time taken by the body to fall 10 and 20 meters? (Take g = 10m/s^2)

The body is released from a height of 100 m and falls freely.
The acceleration on the body is due to gravity and equal to 10 m/s and its initial velocity is 0
m/s.


Now we use the relation y = ut + (1/2) a*t^2 to find the time
taken to travel 10 m and 20 m.


For 10
m:


y = ut + (1/2) a*t^2


=> 10 =
0*t + (1/2)*10*t^2


=> 10 =
5t^2


=> t^2 = 2


=> t=
sqrt 2 s.


For 20 m:


y = ut + (1/2)
a*t^2


=> 20 = 0*t +
(1/2)*10*t^2


=> 20 =
5t^2


=> t^2 = 4


=> t= 2
s.


Therefore we see that the body takes sqrt 2 s to
fall 10 m and 2 s to fall 20m.
The time taken to travel 20 m is not twice that
taken to travel 10 m as the body is accelerating.

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