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 :`m=50 gm=50xx10^(-3)KG`, `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(2gh)` Final velocity, `v=sqrt(2xx9.8xx40)=28 ms^(-1)` `K.E. = (1)/(2)mv^(2)=(1)/(2)xx50xx10^(-3)xx28xx28=19.6 J`