1. Section 8.8
Angular Momentum and Its Conservation

2. Rotational Kinetic Energy
 How do I calculate angular
momentum?
 How do I apply conservation of
momentum to angular momentum?

3. Angular Momentum


4. Conservation of Angular
Momentum


5. • Systems can change their rotational
inertia
• Must be internal forces that change the
rate of rotation
Angular Momentum

6. Example
A small mass m, attached to the end of a
string revolves in a circle on a frictionless
table top. The other end of the string passes
through a hole in the table. Initially, the mass
revolves with a speed v1 of 2.4 m/s. The
string is then pulled slowly through the hole
so that the radius is reduced to r2 = 0.48 m.
What is the speed v2 of the mass now?

7. Homework
 Page 222, # 51 - 56

8. Homework
 Page 222, # 57 - 62