A 72 kg rock is blasted into pieces. One piece has a mass of 29kg and is moving North at 33m/s. What is the velocity of the other piece?

Question

This is a momentum/impulse problem

Answer 1

I assume the block was initially at rest and it broke into exactly 2 pieces.  Solve using conservation of linear momentum.  The initial linear momentum is zero.  We can easily compute the final linear momentum of the first piece.  Then the linear momentum of the second piece must be equal and opposite, and we can get the speed from the momentum.

 

After the explosion,

 

m₁ = 29 kg

v₁ = 33 m/s North

m₂ = (72 - 29) kg = 43 kg

v₂ = ? South

 

Looking just at magnitudes,

 

m₁v₁ = m₂v₂ ⇒

 

v₂ = (m₁/m₂)v₁ = (29/43)(33 m/s) South ≅ 22.3 m/s South