sir , if we throw a ball vertically upwards then at maximum height it has only potential energy stored in it. at a point just above the ground it has max. kinetic energy. then what happens to the energy after the ball comes to rest on the ground?

during the motion of ball its some  energy is consumed by friction in air , when it hits the groung then some energy is lost by friction at surface ...

thus kE of ball is continiously decreasing , now max height attained is smaller than in previous

journey & this all is repeated upto the instant when it completely looses all its KE...

THis energy is lost in the form of heat energy ...

You are right, ideally, the ball should not stop.

But this is not so in real life. Because, practically, all the potential energy is not converted into kinetic energy but some of it is lost in the form of sound or heat energy. Also, the collision of the ball is not perfectly elastic.* i.e,

e is not equal to 1..

Hence, the ball comes to rest after somtime..

*The coefficient of restitution of the ball is not 1. Meaning the velocity with which the ball strikes the ground is not equal to the velocity with which the ball bounces back.

Please Approve!!