1. Circular Motion Section 7.3
Physics

2. Objectives
Explain the acceleration of an object moving in a circle at constant speed.
Describe how centripetal acceleration depends upon the object’s speed and the radius of the circle.
Recognize the direction of the force that causes centripetal acceleration.
Explain how the rate of circular motion is changed by exerting torque on it.

3. Acceleration and Velocity
Acceleration is towards the center of the circle.
Velocity is at a 90°angle to the acceleration.

4. Centripetal Acceleration
The acceleration of an object in uniform circular motion always points in toward the center of the circle: “Center seeking” acceleration – Centripetal Acceleration.
ac = v²/r
Centripetal acceleration equals velocity squared divided by the radius of the path.
ac = (4π²r)/T²
T = Time to complete one revolution.

5. Force Created by Ac Fnet = mac
If we substitute for ac using the previous two equations we get:
Fnet = (mv²)/r
Fnet = m(4π²r)/T²

6. Practice Problems
Page 166
15-16

7. Worksheets
Version 1
Version 2