A body of mass 50 kg is projected vertically upwards with velocity of 100 m/sec. 5 seconds after this body breaks into 20 kg and 30 kg.  If 20 kg piece travels upwards with 150 m/sec, then the velocity of other block will be

Velocity of 50 kg. mass after 5 sec of projection  v=u−gt=100−9.8×5=51 m​/​sAt this instant momentum of body is in upward direction Pinitial=50×51=2550 kg−m​/​sAfter breaking 20 kg piece travels upwards with 150 m/s let the speed of 30 kg mass is V Pfinal=20×150+30×VBy the law of conservation of momentum Pinitial =Pfinal⇒2500=20×150+30×V⇒V=−15 m​/​si.e. it moves in downward direction.