Question

define kinetic energy of body show that the work done is equal to change in kinetic energy of body

Answer 1

energy that depends on speed of a particle is know as kinetic energy or KE..

Kinetic energy = (1/2)*m*v^2

where, m = mass and v = velocity

Change in kinetic energy(dE) = (1/2 )*m*(V^2 -U^2) ………….(*)

where, V = final velocity and U = initial velocity

Also, V^2 - U^2 = 2*a*s ……………….(**) {This expression comes from the laws of motion}

where, a = acceleration and s = distance covered

So, from (*) and (**)

dE = (1/2 )*mass*(2*a*s) = (m*a)*s = F*s {since, Force(F) = m*a}

Thus, dE = F*s = W {since, work done(W) = Force(F) *distance(s)}

Therefore, work done is the change in kinetic energy.

P.S. This is also called work-energy theorem


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Answer 2

The energy which depends on its motion and speed is known as kinetic energy.
Work done is = to the kinetic energy
W=F*S(sq =square root)
Ke=ma*vsq-usq/2a
Ke=m*vsq-usq/2(a is cut )
Ke=M1/2*vsq-usq(u is always 0)
Ke=M1/2*vsq
That so that kinetic energy = to work