An Alternate Solution Using Conservation of Energy

Example 1: Finding the Velocity after an Inelastic Collision - One Object Initially At Rest

A 4.0-kg meatball is moving with a speed of 6.0 m/s directly toward a 2.0 kg meatball which is at rest. The two meatballs collide and stick together. What is their velocity immediately after the (inelastic) collision?

Alternate Solution (Using Conservation of Momentum):

Since no external forces act on the two-meatball system, the system's momentum is conserved. The system's momentum before the collision is:

p_before = m₁v₁ + m₂v₂ = m₁v₁

and the system's momentum after the collision is:

p_after = (m₁ + m₂)v

If momentum is conserved, then:

p_after = p_before

(m₁ + m₂)v = m₁v₁

The velocity of the 6.0-kg meatball immediately after the collision is 4.0 m/s.

This is the "more traditional" solution to the problem.

last update March 21, 2006 by JL Stanbrough