1. Section 2: Centripetal Force

2. Warm-up Video

3. Force Review: Define Force: 2) Define Acceleration:
The acceleration is always in the direction of the ________ ________.

4. Centripetal Force: Force required to keep an object in circular motion.

5. Centripetal Acceleration: Acceleration that is due to the rate of change in direction and acts in the direction of the centripetal force.

6. Centrifuge

7. Centripetal Force Discovery:
What direction is the centripetal force in?
What happens to the force as the angular speed increases?
What happens to the force as the Radius increase?
What happens to the force if the tangential velocity stays the same and radius decreases?

8. Centripetal Force Properties:
Centripetal Force Direction:
2) If the Tangential Velocity increases the centripetal force will:
3) If the Angular Speed increases the centripetal force will:
4) If the radius decreases and the velocity stays constant the centripetal force will:
Draw the force and acceleration on the ball:

9. Reflection:
Which will have the greatest centripetal force?

10. Demo: Upside down water
For the water to stay in the bucket the _________ must be greater than_________.

11. Technology Applications

12. Centripetal Force Equation:
For Centripetal Force “Fc” Fc = m·ac where ac – centripetal Acceleration ac = Vt2/r

13. Sample Problem 1: An 8kg weight is spun at 3m/s at a radius of 1 meter before being thrown. Find the following.
Centripetal Acceleration
b) Centripetal Force

14. Sample Problem 2:
Find the centripetal acceleration at the following locations:

15. Sample Problem 2 Advanced:
Find the normal force on the road at the following two locations for the 100kg cart:

17. Warm-up:
A 4.0 kg ball is attached to 0.7 meter string and spun at 2.0 meters/sec. What is:
a)the centripetal acceleration
b)the centripetal force

18. Warm up: A carnival ride has a radius of 5
Warm up: A carnival ride has a radius of 5.2 meters and spins to keep people suspended on the side wall. If the average coefficient of friction between the people and the wall . 98, find the speed the ride must rotate to sustain suspension.

19. Warm –up: Describe how this ride works.

20. Warm-up Quiz (10pts):
A 2000kg racecar rounds a curve 50 meters in radius at 25m/s. 1) Find the centripetal acceleration: 2) Find the centripetal force:

21. Quiz: Three guys are running at 4m/s around a track.
Who has the greatest tangential velocity?
Who has the greatest angular speed?
Who will pass through the greatest angle in 4 seconds?

22. Quiz 15pts: A 90kg biker round a 20 meter radius bend at 19 m/s
Quiz 15pts: A 90kg biker round a 20 meter radius bend at 19 m/s. Find the following:
Draw the direction of both the centripetal acceleration and force.
Find his centripetal acceleration:
Find his centripetal force:

24. Centripetal Force, Velocity, and Driving

25. Centripetal Force Lab: Tangential Velocity Vs Centripetal Force
Objective: Students will investigate how centripetal force is affected by tangential velocity.
Procedure: Students will complete.

26. Data: Mass of Washer:_________ Mass of Stopper:_________ Radius:_______
# of Washers
Weight of Washers
Time of one revolution
Angular Speed (rad/s)
Tangential Velocity 2 4 6 … 22
Data range: Have the washer count range from 2 to 22
Radius: Use from 20 to 30 cm in radius. You decide.
Angular speed: For best results use around 20 revolutions

27. Analysis:
Must show one sample calculation with correct units for a trial of data.
Use an entire sheet of graph paper and graph centripetal force vs. tangential velocity.
Place a best fit trend line on the graph.
Based on the trend line, explain why how centripetal force is affected by tangential velocity. What mathematical relationship does this model
Is it dangerous to double your velocity while traveling around a bend and why?

28. Teacher Notes
1) Do the first trial together