A bullet of mass 20 g and moving with 600 m/s collides with a block of mass 4 kg hanging with the string. What is velocity of bullet when it comes out of block, if block rises to height 0.2 m after collision?
Linear momentum is a product of the mass (m) of an object and the velocity (v) of the object.
According to conservation of linear momentum
m1 v1 = m1 v + m2 v2
where v1 is the velocity of the bullet before the collision, v is the velocity of bullet after the collision and v2 is the velocity of the block.
∴ 0.02 × 600 = 0.02 v + 4 v2
v2 = 2 m/s
∴ 0.02 × 600 = 0.02 v + 4 × 2
⇒ 0.02 v = 12 - 8
⇒ v =
⇒ v = 200 m/s