1. Rotation and Translation
Angular Displacement
Direction of Angular Displacement
Calculation of Angular Displacement
Comparison of Rotation to Translation

2. Translation
Everything we have done in this class so far is classified as translation.
Translation occurs when a particle or system displaces from one point to another in space.
Objects that translate change their position.
Rotation
We will now discuss rotation.
Rotation occurs when a particle or system turns about a single point.
Objects that rotate change their angle.

3. Angular Displacement
Angular displacement is a vector that determines the direction and magnitude of rotation or revolution of an object.
Its magnitude is the angle through which the object rotated or revolved.

4. The magnitude of the angular displacement is the angle through which an object rotates or revolves
Rotation is shown here

5. The magnitude of the angular displacement is the angle through which an object rotates or revolves
Revolution is shown here

6. Angles have units of radians, revolutions or degrees.
However, they have no dimension.
To convert, we use the following factors

7. The direction of angular displacement is given by the right-hand rule
This is the symbol for a vector pointing out of the page or screen
This is the symbol for a vector pointing into the page or screen

8. Right-hand Rule
Point the fingers of your right hand in the direction of the vector A.
Curl your fingers toward the direction of the vector B.
The cross-product is given by the direction of your thumb. A B

9. For small angles
( ), we can find translational ( ) displacement from the radius vector ( ) and the angular displacement ( )

10. As we will learn later, the translational variables all have rotational counterparts. They are
Name
Translation
Rotation or Angular
Mass (Moment of Inertia) m I
Position r
Velocity v
Acceleration a
Force (Torque) F
Energy K
Momentum p L

11. The equations relating these variables are
Name
Equation
Comment
Mass (Moment of Inertia)
N/A
depends on the geometry of the object
Displacement
Velocity
Acceleration
Force (Torque)
Energy
there is no relationship
Momentum

12. The equations using these variables are mathematically equivalent
For instance