1. Notes on Chapter 10-11 Center of Gravity & Rotational Mechanics
Conceptual Physics
Notes on Chapter
Center of Gravity &
Rotational Mechanics

2. Center of Gravity & Rotational Mechanics
Every object will rotate about a central point…CENTER OF GRAVITY.
Note: Also known as CENTER OF MASS

3. Center of Gravity & Rotational Mechanics
How to find the Center of Gravity (CG).
All of an objects mass acts as if it were concentrated at it’s center.
If you suspend any object, then draw a line beneath. Repeat until you get two lines that cross.

4. Center of Gravity & Rotational Mechanics
Toppling
An object will topple over only when the CG extends beyond the base of support.

5. Center of Gravity & Rotational Mechanics
Stability
The closer the CG is to the base (ground), the more stable an object is said to be.

6. Center of Gravity & Rotational Mechanics
Center of Gravity on People

7. Center of Gravity & Rotational Mechanics
TORQUE
Torque is simply a turning force.
Open a door knob
Tighten a nut with a wrench
Using a Hammer.

8. Center of Gravity & Rotational Mechanics
A torque is produced when a force is applied with Leverage.
Leverage is what is used to apply a force to an object.
This force is applied through the LEVER ARM.

9. Center of Gravity & Rotational Mechanics
TORQUE
TORQUE = FORCE X LEVER ARM
So the same torque can be produced by a large force and a short lever arm … or small force with a large lever arm.

10. Center of Gravity & Rotational Mechanics
Ever try pull a nail with a small or large hammer? Which is easier? Why?

11. Center of Gravity & Rotational Mechanics
Angular Momentum
Angular Momentum is like Linear Momentum – has a vector quantity and magnitude.
Angular Momentum = Rotational inertia x Rotational velocity
Angular Momentum = mass x velocity
Angular Momentum = I ω
Angular Momentum = mvr

12. Center of Gravity & Rotational Mechanics
CONSERVATION OF ANGULAR MOMENTUM
If no unbalanced external torque acts on a rotating system, the angular momentum of that system is constant.