A curved surface is shown figure . The portion BCD is free of friction .There are three spherical balls of identical radii and masses . Balls are released from at rest one by one from A which is at a slighly greater height than C .

with the surface Ab , ball 1 has large eneough friction to cause rolling down without slipping , ball 2 has a small friction and ball 3 has a negligible friction .
(a) For which balls is total mechanical energy conserved ?
(b) Which ball (s) can reach D ?
(c ) For ball which do not reach D, which of the balls can reach back A ?

Explanation

(a) As ball 1 is rolling down withut slipping no disipation of energy is there , total mechanical energy remains unchanged . Hence , it is conserved .
(b) Ball 1 gains rtational energy , ball 2 loses energy due to friction . They cannot cross at C . Ball