This is a famous ques
height=D+9H
soln..
before collison ,both move with √2gH=v
after B2 collides it satrts moving upwrd with v(becoz e=1)
but B1 stilll moves down with v
so vrelative=v-(-v)=2v
after the balls collide with each other,the basket balls speed remains same i.e v upward whereas relative velocity is 2v
so velocity of small ball after collison is in upward direction(becoz mass very small)=2v+v=3v
applying energy conservation
we get height rise=D+(9v2/2g)
but v2=2gH
=> h=D+9H
