The work energy theorem states that work done on a body is equal to the net change in its energy.(P.E or K.E)Proof:Consider a body of mass \\\\(‘m’\\\\) moving with an initial velocity \\\\(u\\\\). Let a constant force \\\\(F\\\\) acting on a body changes its velocity to \\\\(v\\\\). Let \\\\(s\\\\) be the distance traveled.From the equation, \\\\(v^{2} = u^{2} + 2as\\\\),we get \\\\(v^{2} – u^{2} = 2as\\\\)\\\\(\\frac{1}{2}(v^{2} – u^{2}) = as\\\\)Multiplying both sides by \\\\(m\\\\), we have\\\\(\\frac{1}{2}m(v^{2} – u^{2}) = mas\\\\)\\\\(\\frac{1}{2}m(v^{2} – u^{2}) = F.s(\\because F = ma)\\\\)or \\\\(\\frac{1}{2}mv^{2} – \\frac{1}{2}mu^{2} = W\\\\)