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=51m/sAt this instant momentum of body is in upward direction Pintial =50×51=2550kg−misAfter breaking 20 kg piece travels upwards with 150 m/s let the speed of 30 kg mass is V Pfiral =20×150+30×VBy the law of conservation of momentumPinitial =Pfimal ⇒2550=20×150+30×V⇒V=−15m/si.e. it moves in downward direction.