Question

A body of mass 5kg is moving with a 10kg m/s . a force of 0.2N acts on it in the direction of motion of the body for 10s. the increases in in its kinetic energy is

Answer 1

Formula for increased kinetic energy
=1/2 m(v*v-u*u)

But here v : is the new velocity after 0.2 N force applied.

Given :
Momentum - 10kg m/s
Mass - 5kg , so inital velocity ( u )
p = m*u
10 = 5*u
u ( inital velocity of body ) = 2m/s

----------
Now acceleration of Body when force applied on it for 10 sec.

Force = mass * acceleration
0.2 = 5 * acceleration
.So , acceleration = 0.04m/s



So for finding new velocity :

v = u + a*t,
= 2+ 0.04*10
= 2.4m/sec

Then Kinetic Energy = 1/2 m(v*v-u*u)
= 1/2 * 5*( 2.4*2.4-2*2)
= 4.4 joule
=