Question

a force of 20N acting on a body of mass 10kg is found to double its velocity in 8s. Find its initial velocity.

Answer 1

let the initial velocity be u
final velocity,v=2u
f=20  ,  m=10kg   ,  t=8 sec
f=ma
a=f/m
  =20/10
  =2m/s^2
v=u+at
2u=u+2*8
2u-u=16
u=16 m/s

Answer 2

The initial velocity of the body is 16 m/s.

Explanation:

Force acting on the body, F = 20 N

Mass of the body, m = 10 kg

If u is the initial velocity. Then according to given condition, final velocity is 2u. Let us find the acceleration of body first. Force is given by :

F = ma

$a=\dfrac{F}{m}\\\\a=\dfrac{20}{10}\\\\a=2\ m/s^2$

Now using first equation of motion as :

$v=u+at\\\\2u=u+2\times 8\\\\u=16\ m/s$

So, the initial velocity of the body is 16 m/s.

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