Tamash
Using conservation of momentum initial momentum=final momentum about y axis Mv0 *sin90°+0=(3M+M)v sina or. v=v0/4coseca about x axis all parameters are zero
now using conservation of energy about y axia ½M(V0)²=½4M(V0/4)² cosec²a or 4=cosec²a or a=30°
and velocity of centre of mass is V0/4 *cosec30° =V0/2
Answers & Comments
initial momentum=final momentum
about y axis
Mv0 *sin90°+0=(3M+M)v sina
or. v=v0/4coseca
about x axis
all parameters are zero
now using conservation of energy about y axia
½M(V0)²=½4M(V0/4)² cosec²a
or 4=cosec²a
or a=30°
and velocity of centre of mass is
V0/4 *cosec30°
=V0/2
Hope it is right