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)).

A ball of mass 50 g falls from rest vertically downwards through a dis

1.	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)).
Answer» Solution :MASS of ball, m = 50 gm `= 50 XX 10^(-3)` kg , Height of fall, h = 40 m , g = 9.8 `ms^(-2)` From law of conservation of energy, loss in P.E = gain in K.E. `RARR mgh = (1)/(2) MV^(2) and v = sqrt(2 gh)` K.E. = mgh `rArr` K.E. = `50 xx 10^(-3) xx 9.8 xx 40 = 19.6` J Final VELOCITY, `v = sqrt(2 xx 9.8 xx 40) = 28 ms^(-1)`