Transcript Circular Motion Which horse on a merry-go

Circular Motion
Which horse on a merry-go-round
moves faster…
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One on the
outside rail
One near the
inside rail?
Or…how about a turntable?
More than one kind of speed…

Linear speed (velocity)
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Distance  time
Greater for outside horse
AKA tangential speed
Rotational speed (velocity)
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# 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
st
1
Law
 Newton’s 2nd Law

Force needed to cause an
acceleration
A new force…
force – force that
causes an object to follow a
circular path
 Centripetal
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?!!