1 / 33

Circular Motion

Circular Motion. Physics Mrs Coyle . Earth rotates about its axis Satellite revolves about the earth. Part I-Intro to Circular Motion. Tangential Speed and Velocity Frequency and Period Centripetal Force Centripetal Acceleration. Characteristics of Circular Motion.

brittnee
Download Presentation

Circular Motion

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Circular Motion Physics Mrs Coyle

  2. Earth rotates about its axis • Satellite revolves about the earth

  3. Part I-Intro to Circular Motion • Tangential Speed and Velocity • Frequency and Period • Centripetal Force • Centripetal Acceleration

  4. Characteristics of Circular Motion • Tangential (linear) Velocity • Frequency • Period

  5. Frequency, f :#revolutions per unit time • f = # rev / time Units: • (1/sec)=sec-1=Hertz (Hz) • rpm (#rev/min) • rps (#rev/sec) r

  6. Period • Period T : time for 1 revolution • Unit: sec, min, h • Relating Frequency and period • f= 1 T

  7. Arc Length • Arc Length s (unit: meter) • Distance traveled along a circular path. s

  8. Average Tangential (Linear) Speed v= s t Unit: m/s v= 2pr/T = 2prf

  9. Uniform Circular Motion • Linear(tangential speed is constant) • v=constant

  10. Tangential (Linear) Velocity The tangential velocity vector is tangent to the circle at the point of study. v v

  11. Problem 1 A biker travels once around a circular track of radius 20.0m in 3s. Calculate: • the average tangential speed • the frequency • the period Answers: 41.9m/s, f=0.33Hz, T=3s

  12. Record Player

  13. Problem 2 A coin sits 0.10m from the center of a record player spinning at 45rpm. • What is the frequency in Hertz? • What is the period? • What is the linear speed? Answer: 0.75Hz, 1.33s, 0.47m/s

  14. Merry-go-Round

  15. How does the v vary with r? • The linear speed increases as r increases. Example: • How does your linear speed change when you are on a merry-go-round and you move away from the center?

  16. How does the f vary with r? • f does not depend on r Example: • How does your frequency change when you are on a merry-go-round and you move away from the center?

  17. Centripetal Force, Fc= m v2 r • Is a center seeking force. (Always points to the center.) • Is perpendicular to the tangential velocity at any given instant. • It is not an extra force. An existing force represents the centripetal force.

  18. What forces represent the centripetal force in these examples? • Car on bend of road. • Coin on record player. • Child on merry-go-round. • Ball tied on a string.

  19. Centripetal Acceleration, ac= v2 r • Has same direction as centripetal force.(Always points to the center). • Is perpendicular to the tangential velocity at any given instant.

  20. Centripetal Force Fc=mac

  21. Problem 3 A child on a merry-go-round sits 1.5m from the center. They spin 3 times in one min. The mass of the child is 40kg. Find the friction(centripetal force) acting on the child. Answer: 5.9N

  22. Part II More Centripetal Force Problems • Car Rounding a Curve • Loop-the- loop • Rotor

  23. What force plays the role of the centripetal force when a car rounds a curve?

  24. Car Rounding a Bend

  25. Example 1: Car Rounding a Curve • A car is travelling with a speed of 45km/h on a circular horizontal track of radius 50m. What is the minimum coefficient of friction, so that the car stays on the track? • Answer: 0.3

  26. What force plays the role of the centripetal force when a ball is on the top of a loop-the-loop?

  27. Loop the Loop

  28. Example 2: Loop-the-loop • What is the critical velocity of a ball at the top of the loop of radius .3m so that it completes the loop? • Answer: 1.7m/s

  29. Rotor Ride

  30. Rotor Ride • http://www.youtube.com/watch?v=J7k8Oz_73mw&feature=player_embedded#

  31. What force plays the role of the centripetal force in the rotor ride? • http://upload.wikimedia.org/wikipedia/commons/7/7d/Rotormidcyclelunapraksyd.JPG

  32. Example 3: Rotor • A brave student rides in a rotor of radius 5m whose floor drops when it reaches a speed of 20mi/h. What is the coefficient of friction between the student and the wall of the rotor, so that the student does not fall? Answer: 0.6

  33. Recap

More Related