Centipetal force[1]

Centripetal Force

• http://app.discoveryeducation.com/search?Ntt=centipetal+force##

Centripetal Force

• is a force that makes a body follow a curved path

The velocity vectoris always

tangential to the circular path

Constant Velocity

Centripetal Force

• Newton’s 2nd Law– Whenever there is acceleration there is a force to

cause it– the force acts towards the center of the circular

path, the acceleration must also be towards the center

• F = ma

• ac = v2 / r• Fc = mac

WARNING!!!

• Centripetal Force is not a new, separate force created by nature!

• Some other force creates centripetal force– Swinging something from a string tension

– Satellite in orbit gravity

– Car going around curve friction

Challenge!

• How Centripetal Acceleration Keeps an Object Moving in a Constant Circle?

• Velocity constantly changes direction, but not magnitude, when an object is in circular motion.

Conceptual Problem

• What affects Fc more: a change in mass, a change in radius, or a change in speed? why?

• A change in speed since it is squared and the others aren’t.

Conceptual Example

• During a circus trapeze act, a man hangs from a bar and swings his partner from their arms. Which is harder to do: hold the partner still under the bar, or to swing the partner under the bar? Why?

• Swing because not only is there gravity, but there is also centripetal force.

• What provides the Fc?

•Tension their arms.

Centripetal Force

• Newton’s First Law tells us that only a force can cause a body to move out of a straight line path. In circular motion the direction of the body is continually changing at every instant. Therefore a force must be acting. That force is called centripetal (central) force since it acts toward the circle of the circular path.

“Objects in motion tend to remain in motion, at the same rate,And in the same direction, unless acted on by an outside force”

ALL CIRCULAR MOTION REQUIRES A CENTRIPETAL FORCE, OTHERWISE THE

BODY CONTINUES IN A STRAIGHT LINE PATH.

Centripetal Force

• All circular motion requires a centripetal force. Newton’s Second Law of Motion tells us that force equal mass times acceleration. Therefore, centripetal force must produce an acceleration (centripetal acceleration). Since the force acts towards the center of the circular path, the acceleration must also be towards the center !

ALL CIRCULAR MOTION IS ACCELERATED MOTION. THE ACCELERATION IS ALWAYS

TOWARDS THE CENTER OF THE CIRCULAR PATH.