Physics- I need help

Question

Two objects, one with a mass of 20 kg traveling at 30 m/s and the other with a mass of 10 kg traveling at 20 m/s, moving toward each other collide inelastically. What is their velocity after collision?

Answer 1

The answer depends on how inelastic the collision is, which was not stated in the problem.  If the collision is completely inelastic, the 2 masses emerge stuck together, and we can solve the problem.  I will assume that is the case, with the first mass initially moving to the right (+) and the second mass moving to the left (-).

 

Conservation of linear momentum:

 

m₁v₁ - m₂v₂ = (m₁ + m₂)v ⇒

 

v = (m₁v₁ - m₂v₂) / (m₁ + m₂) = [20(30) - 10(20)] / (20 + 10) m/s ≅ 13.33 m/s