A ball of mass m moving with speed V collides with another ball of mass 2m(e=1/2) in a horizontal smooth fixed circular tube of radius R . Time after which next collision will take place is?

Answer 1

assuming conservation of energy, and momentum, calculate the velocitys (and directions) of each ball. Now you know the distance they traverse jointly, 2PIr. So add the velocitie (if the are in opposite direction), (V1+V2)t=2PIr
now if they are in the same direction, subtract, so (V1-V2)t=2PIr
solve for time t.