CH TO HW Begin Date: 11/10/2017 12:00:00 AM -Due Date: 1271/2017 11:59:00 PM End

Question

CH TO HW Begin Date: 11/10/2017 12:00:00 AM -Due Date: 1271/2017 11:59:00 PM End Date: 12/15/2017 12:00:00 AM (17%) Problem 2: Case 1: A DJ starts up her phonograph player. The turntable accelerates uniformly from rest, and takes t 11.7 seconds to get up to its full speed offi - 78 revolutions per minute Case 2: The DJ then changes the speed of the turntable from = 78 to = 120 revolutions per minute. She notices that the 15 times while accelerating uniformly turntable rotates exactly n Randomized Variables t -11.7 seconds n215 times 20% Part (a) Calculate the angular speed described in Case 1, given asfi = 78 revolutions per minute, into units of radians second 20% Part (b) How many revolutions does the turntable make while accelerating in Case 1? 20% Part (c) Calculate the magnitude of the angular acceleration of the turntable in Case 1, in radians second- × 20% Part (d) Calculate the magnitude of the angular acceleration of the turntable (in radians second) while increasing to 120 RPM (Case 2) rade Summary Deductions Potential = | 0.558| 0% 100% 789 HOME sin0 cotan0asin acos0 atan0 acotan sinh0 cosh0 tanh cotanh0 cos tan Submissions ttempts remaining:9 (0 % per attempt) detailed view END 0% O Degrees Radians BACKSPACE DEL CLEAR Submit Hint I give up! Hints: 0% deduction per hint. Hints remaining: 3 Feedback: 0% deduction per feedback. 20% Part (e) How long (in seconds) does it take for the turntable to go from/i = 78 tofz = 120 RPM?

Explanation / Answer

Part D)

120 rpm converts to 12.57 rad/s

Apply wf2 = wo2 + 2(alpha)theta

12.572 = 8.172 + 2(alpha)(2pi)(15)

alpha = 0.484 rad/s2

Part E)

wf = wo + (alpha)t

12.57 = 8.17 + (0.484)(t)

t = 9.09 sec

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