1. Circular Motion
What are some examples of objects taking a circular path?
What force causes those objects to follow that path?

2. Circular Motion

3. Let’s Review First! F=force (N) m=mass (kg) a=acceleration (m/s2)
Remember Newton’s 2nd Law…
F=force (N)
m=mass (kg)
a=acceleration (m/s2)

4. F=ma What is FORCE?
A PUSH
or a…
A PULL

5. Examples of Forces
Tension
Friction
Gravity
Impact Forces

6. F=ma
MASS
The amount of MATTER an object contains. This stays constant.
Not weight - weight changes depending on gravitation field

7. How the velocity changes in a certain amount of time
F=ma
ACCELERATION
How the velocity changes in a certain amount of time
In physics lingo
a=acceleration (m/s2)
Δ= “change in”
v=velocity (m/s)
t=time (s)

8. What is Circular Motion?
Uniform Circular Motion:
movement of an object at a constant speed around a circle with a fixed radius

9. Examples Rollercoaster Swinging an object on a string
Planetary objects - moon, satellites, etc.
Car going around a round-about

10. Circular Motion and Force
If an object stays in its path…
It must have a net force – remember Newton’s 1st Law…
This force is called…
CENTRIPETAL FORCE
centrum: "center" and petere: “go to” or “seek”
So, it’s a “center – seeking” force

11. Examples of these “acting” as the
This is not a new force !!
Examples of forces:
Gravity
Impact Forces
Examples of these “acting” as the
CENTRIPETAL FORCE
Planetary Motion
Rollercoaster
Tension
Friction
Ball on a string
Car going in circles

12. Centripetal Acceleration is…
The acceleration of an object in uniform circular motion. The ac always points toward the center.

13. Finally put it all together…
So, for centripetal force…

14. Remember
The circumference of a circle
C = 2πr
r measured in METERS r

15. Using Period, T, to find velocity
The time it takes an object to make a complete revolution is the PERIOD.
During this time, it travels a distance equal to the circumference of the circle
Remember, v = ∆d/∆t
So, v = 2πr/T

16. What happens when the force is no longer acting
What happens when the force is no longer acting? (Think Newton’s 1st Law)

17. “Critical Velocity”
Is the minimum/maximum velocity needed to maintain the circular path
You can consider vertical motion (like a satellite) or horizontal motion (like a car)
For example, what is the fastest you can go around a curve in your car without losing control; or, what is the minimum speed a satellite needs to stay in orbit?

18. How many g’s?
The g-force references the acceleration of the object relative to free-fall
To determine the number of “g’s” an object experiences, you divide the object’s acceleration by acceleration due to gravity (9.8 m/s2) – it’s a ratio
“g’s” = a/9.8

19. What to remember What circular motion is - recognize it!!!
Newton’s Second Law: F = ma
Velocity can be calculated from period: v = 2πr/T
Centripetal acceleration depends on the object’s velocity and distance from the center of its path
Centripetal force are mass, velocity, and the distance from the center of the path (radius)

20. Let’s do some Calculations
What is an object’s centripetal acceleration if it travels 22 m/s around a circular path with a 0.12 m radius?
An object has a mass of 50 kg, travels in a circular path of radius 1.2 m and rotates 150 revolutions per minute.
Find the object’s velocity
What is the centripetal force on the object?