1. Class Notes for Accelerated Physics
Uniform Circular Motion Review
Class Notes for Accelerated Physics
Mr. Lyzinski
CRHS-South

2. What “could be” on the test?
Using the velocity, period, frequency, acceleration equations to find either v, T, f, or ac.
2) Drawing full FBD’s of: car traveling around a flat, frictionless circular turn
car traveling around a flat, circular turn w/ friction
car/plane traveling around a banked, frictionless turn
a “simple” swing ride (conical pendulum)
a ball on a string in a Horizontal OR Vertical circle
a bike/car/plane doing a loop-de-loop
a bike/car doing a woop-de-doo (dip and/or bump)
a miscellaneous object traveling in a circular path
3) Questions like “What is supplying the centripetal force in ______ situation?”
Skip for accelerated physics

3. What “could be” on the test? (continued)
4) Using the centripetal force equation in each of the following situations
- car traveling around a flat, frictionless circular turn
- car traveling around a flat, circular turn w/ friction
- car traveling around a banked, frictionless turn
- a “simple” swing ride (conical pendulum)
- a ball on a string in a Horizontal OR Vertical circle
- a bike/car/plane doing a loop-de-loop
- a bike/car doing a woop-de-doo (dip and/or bump)
- a miscellaneous object traveling in a circular path
- a plane pulling a banked, circular turn
- finding the critical speed necessary to complete a vertical loop.
Finding the tension in the rope (or the normal force on the track) at the top and bottom of a vertical loop.

4. What “could be” on the test? (continued, again)
Finding the apparent weight (otherwise known as FN) at the bottom of a vertical loop.
Calculating the # of G’s pulled at the bottom of a circular loop
9) Basic knowledge of the terms “Period”, “Frequency”, etc.
10) Finding the maximum speed that you can go before losing contact with the ground on a woop-de-doo bump.
The difference b/w “Centripetal” and “Centrifugal”
Finding the maximum velocity that a ball on a string can swing at, and finding the minimum velocity needed to complete a circular loop.
Skip for accelerated physics

5. Knowing the basic equations
Period – the time needed to complete 1 full revolution.
Frequency – the # of revolutions completed in 1 second.
Velocity – Constant in magnitude for circular motion, but the change in its directions causes the centripetal acceleration.
Centripetal Acceleration – Always directed inward!!!
Centripetal Force – The force that keeps an object (which wants to move in a straight line due to inertia) in circular motion. If an object is moving in a circle, SOMETHING must be supplying the centripetal force.

6. Centripetal vs. Centrifugal
Imagine swinging a rock on a rope. A moving object tends to “remain in motion” and move in a straight line (Newton’s 1st Law!!!!). In order to make the rock move out of a straight line into a circle, you have to keep pulling on the rope. The inward pulling force is the "centripetal" force. But your hand feels the rope pulling it outward. This outward pulling force is called the "centrifugal" force.
HOWEVER, the centrifugal force doesn’t really exist. It is simply the result of the object wanting to remain in motion on its original path (due to inertia). NEVER, EVER use the term or the notion of centrifugal force.
Centripetal force is always directed toward the center of the curve. If centrifugal force did exist (which it doesn’t), it would always be directed away from the center.
Note: Centrifugal means " to flee the center" and Centripetal means "to seek the center"

7. Ball on a string swinging in a horizontal circle
A car traveling around a flat circular turn.
Fg = W = mg T ac FN r mg r Ff FN ac FN ac mg
FN,x
FN,y
What supplies the centripetal acceleration in each case????
A car traveling around a banked, FRICTIONLESS circular turn

8. SKIP FOR ACCELERATED PHYSICS
A car traveling around a banked, circular turn (and wanting to slide down the turn)
A car traveling around a banked, circular turn (and wanting to slide up the turn) FN ac mg
FN,x
FN,y Ff
Ff,x
Ff,y FN ac mg
FN,x
FN,y Ff
Ff,x
Ff,y y x
What supplies the centripetal acceleration in each case????

9. A simple swing ride (conical pendulum)
Ball on a string swinging in a vertical circle
Fg = mg T ac l r R W v T
What supplies the centripetal acceleration in each case????

10. Bike or a car doing a loop-de-loop
Airplane doing a loop-de-loop R W v FN
Forces pointing in are positive. R W v FL

11. Bike or a car doing a woop-de-dooFN mg v
BUMP
DIP
SKIP FOR ACCELERATED PHYSICS

12. For each of the previous FBDs, make sure you can do the following:
answer the question “what is supplying the centripetal force”.
2) write the equation Fc = mac and be able to appropriately fill in the Fc term.

13. Key Equations to know (Horizontal)
Horizontal circles:
Fc = Ff (mFN)
Fc = Tension
Fc = force of adhesion
Fc = force of attraction between 2 objects

14. Key Equations to know (Vertical)
Can you derive each of these equations????
Car doing Loop-de-loop
Ball on String
Plane doing Loop-de-loop
Pilot doing Loop-de-loop
At top
At Bottom
At Side
Critical Speed

15. I’ll re-derive one set of equations for you 
Ball on a string traveling in a vertical circle v mg T
Assuming a constant speed: R
At top: T
At bottom:
Forces pointing in are positive.
At side: mg
If moving too slow, the tension will become zero at the top (the ball will fall )

16. HOMEWORK Uniform Circular Motion Review Packet (all 11 problems)
Solutions will be posted online