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

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

1.	A ball of mass 50g falls from rest vertically downwards through a distance of 40m and hits the ground. Find the kinetic energy and the finaly velocity of the ball before it hits the ground (g= 9.8 ms^(-2)).
Answer» Solution :m= 50 gm `= 50 xx 10^(-3)kg` h= 40m, 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(2gh)` Final velocity, `v= sqrt(2 xx 9.8 xx 40)= 28 ms^(-1)` `K.E. = (1)/(2) mv^(2)= (1)/(2) xx 50 xx 10^(-3) xx 28 xx 28= 19.6J`