A projectile of mass `50 kg` is shot vertically upwards with an initial velocity of `100 m//s`. After `5 s`, it explodes into two fragments, one of which having a mass of `20 kg` travels vertically up with a velocity of `150 m//s`:
a. What is the velocity of the other fragment that instant?
b.Calculate the sum of rnornenta of fragment `3s` after the explosion. What would have been the momentum of the projectile at this instant if there had hem explosion?