A ball of mass 50 g falls from rest vertically downwards through a distance of 40 m and hits the ground. Find the kinetic energy and final velocity of the ball before it hits the ground `(g=9.8 ms^(-2))`.

Explanation

`m = 50 gm = 50 xx 10^(-3) kg,`
h = 40 m, `g = 9.8 ms^(-2)`
From law of conservation of energy
loss is P.E = gain in K.E.
`rArrmgh = (1)/(2) mv^(2) and v = sqrt(2gh)`
Final velocity , `v = sqrt(2xx9.8xx40)=28ms^(-1)`
`K.E. = (1)/(2) mv^(2) = (1)/(2) xx 50 xx 10^(-3) xx 28 xx 28 = 19.6 j`