Name. Date. Period. Engage Examine the pictures on the left. 1. What is going on in these pictures?

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Gregory Taylor
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AP Physics 1 Lesson 9.a Unifom Cicula Motion Outcomes 1. Define unifom cicula motion. 2.

Detemine the centipetal acceleation of an object moving with unifom cicula motion. 4.

Detemine the wok done on an object moving with unifom cicula motion by a centipetal foce. 6.

) Name Date Peiod Engage Examine the pictues on the left. 1. What is going on in these pictues? 2.

In the absence of the foce you descibed in #2., what motion will the peson esume? Obtain one plastic plate with and one without the cut out.

Daw a fee body diagam. 5. Ae the foces balanced o unbalanced? 6. What is the diection of the net foce?

1 AP Physics 1 Lesson 9.a Unifom Cicula Motion Outcomes 1. Define unifom cicula motion. 2. Detemine the tangential velocity of an object moving with unifom cicula motion. 3. Detemine the centipetal acceleation of an object moving with unifom cicula motion. 4. Detemine the centipetal foce exeted on an object moving with unifom cicula motion. 5. Detemine the wok done on an object moving with unifom cicula motion by a centipetal foce. 6. Solve poblems connecting unifom cicula motion and othe concepts peviously addessed (tension, fiction, foces on inclines, etc.) Name Date Peiod Engage Examine the pictues on the left. 1. What is going on in these pictues? 2. What diection do the childen have to exet a foce in ode to emain on the ide? 3. The teache is going to show you a video clip. In the absence of the foce you descibed in #2., what motion will the peson esume? Obtain one plastic plate with and one without the cut out. Spin the steel ball in the plate without the cut out until it follows the oute im. 4. What foces ae acting on the steel ball? Daw a fee body diagam. 5. Ae the foces balanced o unbalanced? 6. What is the diection of the net foce? Spin the ball in the plate with the cut out. 7. What happens to the motion of the ball when it eaches the opening? 8. What type of motion does the ball have? Explain I 9. When the ca eaches point A, the fiction between the ca and the gound dops to zeo. In what diection will the ca tavel afte that point? 10. A ball is spun aound in a hoizontal cicle as shown on the left. What is the diection of the instantaneous velocity and acceleation of the ball at its cuent location? a) b) c) d) 11. What is the diection of the foce exeted on the ball at that location? 1

2 Exploe II Notes Vocabulay List: gavity, fiction, tension, nomal, zeo, cente, net foce, unifom velocity, displacement, V = Δ x / Δ t, magnitude, centipetal motion, acceleating, diection, cicula motion, tangential velocity, 2 π, centipetal foce, I. A. The type of motion that occus when an object moves at a constant speed in a cicula path. B. When an object moves with unifom cicula motion the of the velocity does not change, but the does change. C. ( acceleation) 1. An object expeiencing unifom cicula motion is continuously because its velocity is continuously changing. D. 1. The diection of the change in diection is towad, 1. Given that an object is continuously acceleating, a must be exeted upon it. 2. The diection of the net foce is in the diection of the change in diection, in othe wods, the net foce is towad. E. Motion afte a centipetal foce is discontinued. 1. If a centipetal foce is discontinued, the object moving with unifom cicula motion will is anothe tem fo the instantaneous velocity of an object along the path of unifom cicula motion. II. Unifom Cicula Motion calculations. A. Calculation of velocity on a staight line. 1. V = Δ x / Δ t B. Calculation of a tangential velocity along a cicula path 1. Imagine that a staight line path of length x is looped to fom a cicle of adius =2m. a. What is the value of the path length x? 2. If an object takes 3 seconds to tavel this path, what is the velocity of this object? 2

v 2 c 1. Fc =m a c =m III. Wok and Centipetal Foce A.

This is because thee is no in the diection of the Fc. IV.

In each pictue is the pesence of a centipetal foce, which

Fn = Fc B. Ff = Fc E. Fb = Fc C. Fincline = Fc F.

acceleating. 14. Define centipetal acceleation. 15.

How can the value fo a tangential velocity (vc) be

How can the value of centipetal acceleation be detemined

3 2 π 3. v c = # of otations t C. Calculation of a centipetal acceleation 1. a c = Δv c v c2 = Δt D. Calculation of a centipetal foce using Newton s Second Law. v 2 c 1. Fc =m a c =m III. Wok and Centipetal Foce A. The wok done by any centipetal foce = 1. This is because thee is no in the diection of the Fc. IV. Agents that can exet centipetal foce. In each pictue is the pesence of a centipetal foce, which is ceated by the foce I want you to identify. A. FT = Fc D. Fn = Fc B. Ff = Fc E. Fb = Fc C. Fincline = Fc F. Fg = Fc Explain II Summay 14. Define unifom cicula motion. 15. Define tangential velocity. 16. Explain why an object expeiencing unifom cicula motion is acceleating. 14. Define centipetal acceleation. 15. Define centipetal foce. 16. How can the value fo a tangential velocity (vc) be detemined given the adius and time of otation? 17. How can the value of centipetal acceleation be detemined given the tangential velocity and the adius of motion. 18. How can the value fo a centipetal foce be detemined given the mass of an object and its tangential velocity? 19. How much wok is done by any centipetal foce? 20. What agents can exet a centipetal foce? 3

Exploe III In this activity, you will pedict the elationship between an exeted centipetal foce and the value of the centipetal acceleation of a system.

You will whil the ubbe stoppe aound with unifom cicula motion. (The motion is unifom when the distance fom the stoppe to the tube emains constant).

My Pediction If the centipetal foce is inceased while the adius is held constant, the centipetal acceleation will.

Exeted on Rubbe Stoppe F c = (F t 2 w stoppe 2 ) Rubbe Stoppe Mass (kg) Pedicted Centipetal Acceleation F c a c = m ubbe stoppe (m/s 2 ) Data Table II Tial 1 Time fo 10 evolutions Set up A B C D E

4 Exploe III In this activity, you will pedict the elationship between an exeted centipetal foce and the value of the centipetal acceleation of a system. You will hang mass hanges fom a thead that passes though a smooth plastic tube. At the othe end of the thead you will attach a ubbe stoppe. You will whil the ubbe stoppe aound with unifom cicula motion. (The motion is unifom when the distance fom the stoppe to the tube emains constant). The impotant measuements you will make ae The weight of the hanges. The adius of the cicula path. The time it takes the ubbe stoppe to complete 10 evolutions. The mass of the ubbe stoppe. 21. My Pediction If the centipetal foce is inceased while the adius is held constant, the centipetal acceleation will... Complete the following data tables Data Table I Set up Numbe of Hanges A 2 B 3 C 4 D 5 E 6 Mass of Hanges (kg) Weight of Hanges w=mg (N) Tension Exeted on Rubbe Stoppe w=f T (N) Centipetal Foce Exeted on Rubbe Stoppe F c = (F t 2 w stoppe 2 ) Rubbe Stoppe Mass (kg) Pedicted Centipetal Acceleation F c a c = m ubbe stoppe (m/s 2 ) Data Table II Tial 1 Time fo 10 evolutions Set up A B C D E Tial 2 Time fo 10 evolutions Tial 3 Time fo 10 evolutions Aveage Time fo 1 evolution Radius (m) Tangential Velocity v c = 2π t (m/s) Obseved Centipetal Acceleation a c = v c 2 (m/s 2 ) Explain III 22. Why would you time ten (10) evolutions when you ae only using the time fo one in you calculations? Plot the centipetal foce fom the fist table and the centipetal acceleation fom the second data table on the gid on the ight. 22b. What is the appaent elationship between the centipetal foce exeted on the stoppe though tension and the centipetal acceleation of the ubbe stoppe? 23. Was you initial pediction suppoted o has you thinking changed? 4

5 24. Qualitatively compae the pedicted centipetal acceleations and the obseved centipetal acceleations. 25. What ae the units of the slope of this line? 26. What is the value of the slope of this line? 27. Compae the slope to the mass of the ubbe stoppe. 28. Pepae a fee body diagam fo he ubbe stoppe as it was whiled about with unifom cicula motion in the space below. 29. What component of the tension was not consideed in this expeiment? 30. What othe souces of eo wee pesent in this expeiment? 5

Uniform Circular Motion

Uniform Circular Motion Unifom Cicula Motion Intoduction Ealie we defined acceleation as being the change in velocity with time: a = v t Until now we have only talked about changes in the magnitude of the acceleation: the speeding