Circular Motion

Which horse on a merry-go-round moves faster… One on the outside rail One near the inside rail?

Or…how about a turntable?

More than one kind of speed… Linear speed (velocity) Distance  time Greater for outside horse AKA tangential speed Rotational speed (velocity) # of rotations per unit of time Same for all horses AKA angular speed

Interesting application… Rims of train wheels are tapered

Washer on a string… The washer’s speed does not change, but its velocity does Centripetal acceleration

What would Isaac say? Newton’s 1st Law Newton’s 2nd Law Force needed to cause an acceleration

A new force… Centripetal force – force that causes an object to follow a circular path

What’s wrong with this picture?

Be careful… Centripetal force sometimes called “centrifugal” force A “fictitious” force

Quick Check… What is the direction of the force that acts on clothes in a washing machine? a. outward b. inward C. up D. down

If you whirl a tin can on the end of the string and the string suddenly breaks, the can will ______________. A. fly directly away from you b. fly directly toward you c. fly off, tangent to its circular path d. spiral away from your hand e. spiral in toward your hand

Which has the greatest angular speed – the horse on the inside or the outside of the merry-go-round? Or is this a trick question?!!