AP Centripetal Acceleration Lab

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Lawrence Barrett
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1 AP PHYSICS NAME: PERIOD: DATE: GRADE: DEVIL PHYSICS BADDEST CLASS ON CAMPUS AP Centipetal Acceleation Lab Note: Data collection will be done by table goups. Data analysis is to be done individually. Copying a data analysis foomeone else o allowing someone else to copy you wok will esult in a zeo fo the assignment and a efeal to the IB Coodinato fo cheating. Discussion: This lab will exploe centipetal acceleation using a device simila to the one in the diagam to the ight. The device consists of a PVC tube, a lead weight and a ubbe stoppe. The weight and stoppe ae connected by 40lb test fishing line. The object of this execise is to expeimentally detemine the velocity and centipetal acceleation of the ubbe stoppe and then compae it to the theoetically detemined value. The stoppe will be otated at a given adius fo a given peiod of time while the weight emains at a constant distance fom the tube. The tension in the sting needed to ceate the centipetal acceleation of the stoppe is equal to the tension needed to keep the weight in a constant position. Fom the data collected you will compute velocity and centipetal acceleation of the stoppe and then compae them to the theoetical values. Refeence the fee-body diagams below fo the weight and the stoppe: FT FT Fg = mwg ac = v2 If we apply Newton s Second Law to the fee-body diagams, fo the weight we get, F T = F g = m w g Fo the stoppe we get, F T = Combining the two equations we get, = m wg If we then solve fo the velocity of the stoppe we get, = m wg v = m wg AP Centipetal Acceleation Lab.Docx Updated: 8-Dec-15 Page 1 of 5

2 This gives you the theoetically detemined value. Velocity is also equal to distance divided by time. Fo cicula motion, the distance tavelled is equal to the cicumfeence and the time is the time fo one evolution (the peiod). To minimize eo, we will time fo seveal evolutions and then divide by the numbe of evolutions to get an aveage time fo one evolution. v = Mateials: 2π (time #ev) Safety goggles (1 pe peson) Time (1 pe table goup) Mete Stick (1 pe table goup) Pocedue: Stip of masking tape (1 pe table goup) Centipetal Acceleation Appaatus (1 pe table goup) 1. All table goup membes must don safety goggles and wea them thoughout the entie expeiment. Thee is potential fo the sting to beak and fo the stoppe to stike you. 2. Pull on the stoppe until you have a adius of 40cm (0.40 m) fom the cente of the tube to the appoximate cente of mass of the stoppe. Have a lab patne place a small piece of masking tape on the line just below the tube on the weight side of the tube. This will act as a make to maintain the 40 cm adius and the weight in the same position below the tube. 3. One peson should pactice spinning the stoppe at a speed that will maintain the masking tape make at the bottom of the tube. Be caeful not to stike othe students that you like. 4. When the spinne feels confident, a second peson will stat the time. A thid peson counts the evolutions. Stop the time afte 50 evolutions and ecod the time in seconds. Thee will be some andom eo in maintaining the desied adius/weight height. Howeve, timing fo 50 evolutions should minimize this eo. 5. Change job esponsibilities among you table goup and epeat steps 3 and 4 fo a total of thee tials at a 40cm adius. 6. Repeat steps 1 though 5, using a 50cm adius. Accomplish thee tials fo each adius. Data Collection (3/ ) Mass of weight = 27.4g (0.0274kg) Mass of stoppe = 6.77g ( kg) Radius = 40cm: Radius = 50cm: Radius = 60cm: Tial Time fo 50 Tial Time fo 50 Tial Time fo Avg. Avg. Avg. AP Centipetal Acceleation Lab.Docx Updated: 8-Dec-15 Page 2 of 5

3 Data Analysis: 1. Compute an aveage time fo 50 evolutions fo each of the thee adii and place it in the table above. 2. Detemine the cicumfeence of the cicula motion using C = 2π and ecod it in the chat below. Do this fo all thee adii. 3. Detemine the time pe evolution by taking the aveage total time fo all evolutions and dividing by the numbe of evolutions. Do this fo all thee adii. 4. Calculate the expeimental velocity at each adius by dividing the cicumfeence by the time pe evolution. Do this fo all thee adii. 5. Calculate the expeimental centipetal acceleation of the stoppe using the expeimentally detemined velocity in the equation, a c = v2 fo all thee adii. 6. Calculate the theoetical velocity of the stoppe using, v = m wg fo all thee adii. 7. Calculate the theoetical centipetal acceleation of the stoppe using the theoetically detemined velocity in the equation, a c = v2 fo all thee adii. Expeimental Data (1/4 point each, total = 5/ ) Theoetical Data Radius mweight (kg) Mstoppe (kg) Cicumfeence (m) Time/Rev v (m/s) ac (m/s 2 ) v (m/s) ac (m/s 2 ) 0.40 m m m (6/ ) Calculate the pecent diffeence between the theoetical and the expeimental values using ( Expeimental Theoetical ) x100% and ecod you answes in the chat below. Theoetical 40 cm 50 cm 60 cm Velocity % Diff. Centipetal Accl. % Diff. 9. (1/ ) Wee you expeimental values geneally highe o lowe than the theoetical values? Explain why you think this is so. AP Centipetal Acceleation Lab.Docx Updated: 8-Dec-15 Page 3 of 5

4 The value you used fo the adius in you calculations was based on the measued distance fom the cente of the tube to the cente of the stoppe. This would be tue if the stoppe was otating hoizontally. This cannot happen because thee would be no vetical component of the tension foce to suppot the weight of the stoppe. You can see fom the dawing that the actual adius (distance fom the stoppe to the axis of otation) is slightly less. You can find the actual adius by using the equations below: F T y = F g s = g F T x = sinθ = g m w g = m w θ = sin 1 m w F T = m w g cosθ = actual measued measued cosθ = actual actual θ F T=m wg measued F T-y=F g-s F g-s=g Fo expeimental data, the actual angle between the otating stoppe and hoizontal should be measued, but fo this expeiment it is impactical. measued 10. Calculate the angle θ and actual adius using the equations above and find the cicumfeence based on this new adius. 11. Re-calculate the expeimental and theoetical velocity and centipetal acceleation as you did befoe, but this time use the "actual" adius as calculated above. Mstoppe (kg) mweight (kg) 0.40 m Expeimental Data (1/4 point each, total = 6/ ) θ actual "New" Cicumfeence (m) Time/Rev (unchanged) v (m/s) ac (m/s 2 ) Theoetical Data v (m/s) ac (m/s 2 ) 0.50 m m (6/ ) Calculate the pecent diffeence between the theoetical and the expeimental values using ( Expeimental Theoetical ) x100% and ecod you answes in the chat below. Theoetical 40 cm 50 cm 60 cm Velocity % Diff. Centipetal Accl. % Diff. 13. (1/ ) Did the pecent diffeences between expeimental and theoetical incease o decease? AP Centipetal Acceleation Lab.Docx Updated: 8-Dec-15 Page 4 of 5

5 14. (1/ ) Wee you new expeimental values geneally highe, lowe o just about the same as the theoetical values? Explain why you think this is so. 15. (3/ ) List thee potential souces of eo in this expeiment: a. b. c. 16. (3/ ) List thee ways in which the accuacy of this expeiment could be impoved: a. b. c. This data was collected (cicle one) by myself / a team. I paticipated fully and equally in the collection of this data and ecoded it myself. The answes on this lab ae a poduct of my own wok and effot. Though I may have eceived some help in undestanding the concepts and/o equiements, I did the wok myself. Student Signatue (fo electonic submission, type student numbe in lieu of signatue) ROOM FOR IMPROVEMENT APPLICABILITY: This lab is best suited fo (check all that apply): Pe-DP Physics IB Physics 2 IB Physics 3 None of These IMPROVEMENT: This lab can be impoved by: AP Centipetal Acceleation Lab.Docx Updated: 8-Dec-15 Page 5 of 5

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

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