**Circular Motion - Ch. 6.2**

Centripetal Accleration

Since the acceleration vector of an object in uniform circular motion points in towards the center, its acceleration is named Centripetal (or "center-seeking") Acceleration.

Centripetal Force

There must be some physical force pushing or pulling the object towards the center of the circle. This is the centripetal force requirement.

**Recap**

Objects must accelerate to travel in circular motion.

The net force required to cause an object to accelerate in circular motion is called the centripetal force

Centripetal literally means "center-seeking" because the net force of an object traveling in circular motion must be directed inward.

Uniform Circular Motion:

-Speed is constant

-Direction is changing

Acceleration and UCM

Uniform Circular Motion

Is an object in uniform circular motion accelerating?

Acceleration and UCM

What is this acceleration called?

Centripetal Acceleration

Where ac = centripetal acceleration (m/s2)

v = tangential speed (m/s)

r = radius (m)

"Forces cause Accelerations"

So, if an object in uniform circular motion is accelerating, it must have some net force acting on it. What's that called?

We are not introducing a new type of force but rather describing the direction of the net force acting upon the object which moves in the circle.

Whatever the object, if it moves in a circle, there is some force acting upon it to cause it to deviate from its straight-line path, accelerate inwards and move along a circular path.

Centripetal Force

So, for an object in uniform circular motion, Newton's Second Law get's restated as:

Where Fc = Centripetal Force (N)

m = mass (kg)

ac = centripetal acceleration (m/s2)

*This equation is derived on p. 154 of your text.

Topics

Name that centripetal force

Any curve will do

Squish the jelly

Centrifugal force

The loop-the-loop

Questions?

Name that Centripetal Force

Any Curve will do

Squish the Jelly

http://www.physicsclassroom.com/mmedia/circmot/rht.cfm

The vertical loop-the-loop

Centrifugal Force

Name given to the force which seems to act outward on objects undergoing circular motion.

For an inertial frame of reference - this is a nonexistent or "fictitious" force.

Questions?

Yes!

This is the acceleration required for an object to complete circular motion