Circular Motion Chapter 10

10.1 Rotation & Revolution Turning around an internal axis is rotation Turning around an external axis is revolution Earth does both!!

10.2 Rotational Speed Where do you move the fastest? On the out side of a merry-go-round or on the inside?

Answer: **It depends on what type of speed you are talking about

Question: At an amusement park, you and a friend sit on a large rotating disk. You sit at the edge and have a rotational speed of 4 RPM and a linear speed of 6 m/s. Your friend sits halfway to the center. What is her rotational speed? What is her linear speed?

Answer: her rotational speed is 4 RPM and her linear speed is 3 m/s

Tangent A tangent is a line that touches a circle at one point So for circular motion, tangential speed is the same as linear speed

Rotational Speed What’s the difference between rotational and tangential speed? Rotational speed is the # of rotations per unit of time Tangential speed is linear speed along a circular path

Tangential speed Tangential speed is directly proportional to the radial distance x rotational speed or V ~ rω

10.3 Centripetal Force Means “aiming at center” it is an inward force The force you feel when are pushed to the wall in a ride. (force of the wall on you) Constant acceleration

Centripetal Force Example

Six Flags

10.4 Centrifugal forces Means “center fleeing” The force that pushes you away from the curve.

Centrifugal Force It is Inertia

10.6 Centrifugal Force Revealed It is a result of rotation. It is not part of an interaction It is not a true force