Work Energy And Power Question 106
Question: 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 [RPMT 1999]
Options:
A) 15 m/sec downwards
B) 15 m/sec upwards
C) 51 m/sec downwards
D) 51 m/sec upwards
Show Answer
Answer:
Correct Answer: A
Solution:
Velocity of 50 kg. mass after 5 sec of projection $ v=u-gt $
$ =100-9.8\times 5=51\ m/s $
At this instant momentum of body is in upward direction $ {P _{initial}}=50\times 51=2550\ kg-m/s $
After breaking 20 kg piece travels upwards with 150 m/s let the speed of 30 kg mass is V $ {P _{final}}=20\times 150+30\times V $
By the law of conservation of momentum $ {P _{\text{initial }}}={P _{final}} $
therefore $ 2500=20\times 150+30\times V\Rightarrow V=-15\ m/s $
i.e. it moves in downward direction.
