**Goal:** Developing a strategic approach to problem solving

**Source:** CT151.2S02-44 spinoff

A cart

of mass 2m collides and sticks to a cart of mass m that is initially at

rest. The combination of the two then moves together. Which of the

following principles would be the most efficient way to find the final

speed of the combination?

- The Work/Energy Theorem
- Newton’s Laws and the basic equations of motion
- Conservation of Energy
- Conservation of Momentum
- Conservation of Angular Momentum
- A different principle entirely.
- Two (or more) of them would be equally efficient.
- Need more information.

## Commentary:

## Answer

(4) It is valuable to always associate conservation of momentum

with the third law. In addition, it is worthwhile to distinguish totally

inelastic collisions from typical inelastic collisions.