1. Uniform Circular Motion
Chapter 10

2. Circle
Circumference
C = π D = 2 π r
Area
A = π r2

3. Rotation vs. Revolution
When an object turns about an internal axis
The Earth rotates creating day and night
Revolution
When an object turns about an external axis
The Earth revolves around the Sun

4. Speed Linear Speed Tangential Speed Rotational Speed
Distance traveled per unit time
Tangential Speed
Speed of something moving in a circular path
Speed is directed tangent to the circle
Rotational Speed
Number of rotations per unit time (Angular Speed)

5. Centripetal Force, Fc Fc
Force that keeps an object moving in a circular path
Directed towards center of circle
Without it, object would continue in a straight line (N1L) Fc

6. Centripetal Acceleration
Change in velocity (magnitude or direction) that keeps object moving in a circle
Directed towards center of circle

7. Centripetal Force, Fc

8. Centripetal Force, Fc Centripetal Force is provided by another force
Tension provides Centripetal Force T Fg

9. Centripetal Force, Fc At top, weight provides Centripetal Force
At bottom, Normal Force provides Centripetal Force FN Fg

10. Centrifugal Force Not Real, Does not exist Result of Inertia (N1L)
Imagine a box sitting on the front seat of an old car with vinyl bench seat

11. Centrifugal Force
While car is moving forward, box’s inertia is moving forward
As car turns left, box continues forward, appears to move right

12. Centripetal Force Example
A 50kg skater going around a 10m curve at 10m/s. What is the centripetal force?

13. Another Example
How fast is a 1200kg car moving around a 100m curve to have a centripetal force of 7500N?