Question

A bullet of mass 7g is fired into a block of metal weighing 7kg.The block is free to move.After the impact the velocity of the bullet and the block is 0.7 m/s.What is the initial velocity of the bullet?

Answer 1

$mv = p$

So from this formula,

momentum of bullet = 7*v=7v

momentum of block = 7*0.7=4.9kgm/s

therefore from the law of conservation of momentum we know that,

7v = 4.9kgm/s

=> v = (49/10)/7

=0.7m/s