1. Circular Motion

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

3. Or…how about a turntable?

4. 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

5. Interesting application…
Rims of train wheels are tapered

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

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

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

9. What’s wrong with this picture?

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

11. 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

12. 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

13. 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?!!