Circular Circular MotionMotion

Centri____ ForceCentri____ Force

Frequency vs. Period Period (T)- The time it

takes for one full rotation or revolution of an object in seconds.

Frequency (f)- The number or rotations or revolutions per unit time, measured in Hertz (Hz)

1 1T f

f T

How do we get

this equation?

2T

rv

T

Tangential Speed

CentriCentripetalpetal Force F Force Fcc

A force of some kind is required to A force of some kind is required to maintain circular motion. Why?maintain circular motion. Why?

Any force that causes an object to Any force that causes an object to follow a circular path is called a follow a circular path is called a centripetal forcecentripetal force..

Centripetal means “center-seeking”Centripetal means “center-seeking”Always acts inwardsAlways acts inwards

Centripetal Centripetal Acceleration aAcceleration acc

2T

c

va

r

Tangential Velocity

Radius

Centripetal ForceCentripetal Force

2

2

c c

c

Tc

F ma

F ma

va

r

mvF

r

ExamplesExamples

Friction is the centripetal force acting Friction is the centripetal force acting on a car driving around a curve.on a car driving around a curve.

Gravity is the centripetal force Gravity is the centripetal force causing the moon to orbit the Earth. causing the moon to orbit the Earth.

Centripetal force is not a new type of Centripetal force is not a new type of force. force. It is just the name given when a It is just the name given when a force causes circular motionforce causes circular motion by acting by acting at a right angle to an object’s motion.at a right angle to an object’s motion.

A ball is attached to a string and is A ball is attached to a string and is spinning in a circle. The string spinning in a circle. The string breaks. Why does it fly off at a breaks. Why does it fly off at a

tangent?tangent? Because NO FORCE acts upon it!Because NO FORCE acts upon it!

Centrifugal force is a Centrifugal force is a fictitious forcefictitious force. It is an . It is an effect of rotation. effect of rotation.

How might centrifugal force replace How might centrifugal force replace gravity?gravity?