A bullet of mass `7kg` is fired into a block of metal weighing `7kg` The block is free to move Caluculte initial velocity of the bullet if the velocity of the block with the bullet in is `0.7m//s` .

Answer

`700.7m//s` .

Explanation

According to the principle of conseration of linear momentum,
linear momentum lost by bullet = linear momentum gained by block with bullet inside
`(7)/(1000) xxupsilon =(7 + (7)/(1000))xx 0.7`
`upsilon = (7007)/(1000) xx (0.7 xx 1000)/(7) = 700.7 m//s` .