Question

Write an expression for kinetic energy of a moving body and hence deduce work energy theorem

Answer 1

Kinetic energy of a moving body =1/2mv^2 joule.

Let an object starts moving with initial velocity (u) =0 and final velocity (v) =V m/s .In time t sec the the displacement of the body is S m and the acceleration (a) =a.
Note :-the mass of the body be m kg.


Using 3rd equation of motion,
v2 = u2 + 2as
V2= 0+ 2as
s =V2/2a .......................(1)
Now , change in kinetic energy =1/2mv2 - 1/2 u2 joule
=1/2mV2 joule ......(2)
Now , work done =Fs joule = ma ×s joule
=ma×( V2/2a)..........using (1)
=1/2mV2 joule............(3)
Using (2) and (3) we get ,
Work done = change in KE