2. When you ride the Spindletop, you move in a circle at a constant speed
When you ride the Spindletop, you move in a circle at a constant speed. In what direction is the force that acts on you to keep you moving in a circle?
A) Directly towards the center of the circle
B) Directly away from the center of the circle
C) Along the direction of your motion
D) At an angle between your direction of motion and the center of the circle

3. Uniform Circular Motion

4. Uniform Circular Motion

5. Uniform Circular Motion
“Centripetal acceleration”

6. Uniform Circular Motion
“Centripetal acceleration”
“Centripetal force”

7. Uniform Circular Motion
What provides the centripetal force when I twirl a weight on a string over my head?

8. Uniform Circular Motion
What provides the centripetal force on the Moon as it orbits the Earth?

9. Uniform Circular Motion
Why do they bank the turns of a race track?

10. Uniform Circular Motion
In a flat turn, what force provides the centripetal force?

11. A 1200 kg car rounds a corner of radius r = 45 m
A 1200 kg car rounds a corner of radius r = 45 m. If the coefficient of static friction between the tires and the road is ms = 0.82, what is the greatest speed the car can have in the corner without skidding?

12. If a roadway is banked at the proper angle, a car can round a corner without any assistance from friction between the tires and road. Find the appropriate banking angle that will allow a car traveling at 20.5 m/s in a turn of radius 85.0 m to safely round the turn on a sheet of ice.

13. Normal force in a dip in the road
is greater than the weight of the car

14. Centrifuge

15. Centrifuge
A centrifuge with a radius of 8.50 cm rotates at 5750 rpm. What is the acceleration of a point on the outer edge of the centrifuge?

16. Centrifuge

17. © 2017 Pearson Education, Inc.
You’re on a Ferris wheel moving in a vertical circle. When the Ferris wheel is at rest, the normal force N exerted by your seat is equal to your weight mg. How does N change at the top of the Ferris wheel when you are in motion?
N remains equal to mg
N is smaller than mg
N is larger than mg
None of the above
Answer: B
© 2017 Pearson Education, Inc.
Going in Circles

18. © 2017 Pearson Education, Inc.
You’re on a Ferris wheel moving in a vertical circle. When the Ferris wheel is at rest, the normal force N exerted by your seat is equal to your weight mg. How does N change at the top of the Ferris wheel when you are in motion?
N remains equal to mg
N is smaller than mg
N is larger than mg
None of the above
You are in circular motion, so there has to be a centripetal force pointing inward. At the top, the only two forces are mg (down) and N (up), so N must be smaller than mg.
Follow-up: Where is N larger than mg?
© 2017 Pearson Education, Inc.
Going in Circles