a rod of mass m and length 21 could rotate with the axis through its center in the vertical plane,the rod was along the horizon initially,a ball of mass m hit one end of the rod with speed u.the collision is elastic,Find the speed of the ball bouncing back and the angular velocity of the rod? 0 Solution: -mul =-Ja+mvl 2 mu= 2 m+2 u(M-3m） 6mu V= M+3m (M +3m)l a rod of mass m and length 2l could rotate with the axis through its center in the vertical plane，the rod was along the horizon initially，a ball of mass m hit one end of the rod with speed u.the collision is elastic,Find the speed of the ball bouncing back and the angular velocity of the rod? o u Solution:  mul  J  mvl 2 2 2 2 1 2 1 2 1 mu  mv  J M m u M m v 3 ( 3 )    M m l mu ( 3 ) 6   