A particle of mass m, resting on a smooth horizontal table, is hit by another particle of mass M, the speed of the impact being u. The impact is perfectly elastic, and the particle of mass m moves in...

A particle of mass m, resting on a smooth horizontal table, is hit by another particle of mass M, the speed of the impact being u. The impact is perfectly elastic, and the particle of mass m moves in a direction making an angle β with the direction of u after the impact. Find out the speed of the particle of mass m.