A body of mass 500 g initially at rest is moved by a horizontal force of 1 N. Calculate the workdone by the force in 20s and show that is equal to the change in kinetic energy of the body.

Explanation

Mass of a body `(m)=(500)/(1000)kg=0.5 kg`
Horizontal Force (F) = 1 N
Time (t) = 20s.
Therefore, acceleration of a body.
`a=F//m=(1)/(0.5)=2ms^(-2)`
Distance trayelled `s=ut+(1)/(2)at^(2)`
`s=0xx20+(1)/(2)xx2xx(20)^(2)=0+(1)/(2)xx400xx2`
Displacements = 400 m
Workdone `= F xx s = 1xx400`
`= 400 J , v = u + at = 0 + 2 xx 20`
`v = 40`
Change in K.E. `=(1)/(2)m(v^(2)-u^(2))`
`=(1)/(2)xx0.5xx(40^(2)-0)=(1)/(2)xx0.5xx1600`
`= 400 J`