Two identical balls A and B are moving as shown in the fig. Ball A hits a smooth floor head on with a velocity u and at the same instant ball B strikes A head on with a horizontal velocity u. The collision between A and B is perfectly inelastic whereas the coefficient of restitution for collision between A and the floor is `e = 0.5`. At what time the two balls will collide again? Assume friction to be absent everywhere.

Answer

A time `(u)/(g) after first collision