Chapter 6Motion in Two Dimensions

Section 6.2Circular Motion

How do I explain why an object that is moving in a circle at constant velocity has acceleration?

How can I calculate centripetal acceleration?

How can I identify the forces that cause centripetal acceleration?

Uniform Circular MotionA mass being rotated at a constant velocity

Uniform Circular MotionVelocity is constant

The velocity vector is constantly changing direction

This change in direction provides an acceleration towards the center of the circle

Centripetal Acceleration

This acceleration results from the spinning action, it does not cause the spinning

If the stopper’s speed is 1.5 m/s and the radius is 0.56 m, what is the centripetal acceleration?

Circular VelocityWhat if they do not give you velocity in m/s?

How about 33 rpm?

T = Period = the time needed to turn 1 complete revolution

What is the T for a 33 rpm record?

Centripetal Acceleration

What if a penny was placed on the outside of a record being played at 33 rpm, what would its acceleration be? Use 0.15 m for the radius.

Centripetal ForceSince the acceleration points towards the center,

the centripetal force points towards the center

F = ma, so Fc = ?

Fc is the result of another force that turns the object in a circle

This force can be supplied by tension or friction

Centripetal ForceSupplied by tension

A 13 g stopper is attached to a 0.93 m string. The stopper is swung in a horizontal circle, making one revolution in 1.18 s. Find the tension force exerted by the string on the stopper.

Centripetal ForceSupplied by friction

A car traveling 15 m/s is going around a turn of radius 30 m. What is necessary for the car to stay on the road?

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