1. Uniform Circular Motion
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2. Uniform Circular Motion
Constant speed
Constant radius
Continuous acceleration of a constant magnitude directed radially toward the center
Speed = circumference/period
S=2pr/T

3. UCM Lab
What is the mathematical relationship between net centripetal force (N) and speed(m/s) for an object undergoing UCM?
Consider: If the independent variable is zero, should the dependent variable be zero?

4. PLQ

5. Understanding the Lab
What happened to the net centripetal force when the speed doubled?
What would have happened to the net centripetal force if one could have kept the speed of the stopper constant, but doubled the radius?
What would have happened to the net centripetal force if one could have kept the speed of the stopper constant, but doubled the mass?

6. After Quiz (Not done in 2019)
Gizmo: Uniform Circular Motion Split your lab group in two. One finds the mathematical relationship between SFc and radius, the other finds the relationship between SFc and mass. Put your data, graph and equation on WB.

7. Graphs Showing relationships:

8. Equations for UCM
S=2pr/T
ac = S2/r
SFc = m(S2/r)

9. Ex 1
The blades of a blender are 3.0 cm long. The blender spins at a maximum rate of 80 revolutions per second. Determine the speed and acceleration of the tips of the blades.

10. Ex 2
A 20.0 kg child rides on the edge of a 10.0 m diameter carrousel that makes one revolution every 8.00 seconds. Compute the net force acting on the child. What is the direction of that force? If the child was standing on the deck of the carrousel, what type of force would provide the net force?

11. Freebody exercise 10

12. UCM Problems, where SFc gets expanded
ID what you must find
Draw a FBD
ID the inward force
(Deal with the vertical forces if necessary)
Use SFc = m(S2/r)
Sub and solve

13. Ex1
How fast can a 1200kg car travel around a 100m radius arc if the coefficient of _______ friction is 0.8?
What if the car’s mass doubled, but all other factors remained the same?

14. Ex2
The Taz Twister is a ride at Great Adventure that consists of a round room with carpeted walls. Once the room is up to speed the floor is lowered, but the riders, who feel “pinned to the wall” do not drop with the floor. If the radius of the room is 7.0m, and the coefficient of ______ friction between the riders and the wall is 0.5:
what speed must the riders have to stay “glued to the wall”?
what Period must the ride have?