**Goal:** Develop a strategic approach to problem solving.

**Source:** UMPERG

A bug walks on a rotating disk. Given: M_{bug},

I_{disk}, R_{disk}, and ω_{o} when the bug

is at r_{1}. The bug crawls to r_{2}. Find

ω_{final} for the system.

What principle would you use to solve the problem MOST EFFICIENTLY?

- Kinematics only
- F = ma or Newton’s laws
- Work-Energy theorem
- Impulse-Momentum theorem
- Angular Impulse-Angular Momentum theorem
- Not enough information given

## Commentary:

## Answer

(5) This problem helps students develop a principle-based approach to

problems. Many students may think correctly that this is a conservation

of angular momentum problem and not recognize that the general principle

is the angular impulse – angular momentum theorem.