HW15_Solutions - hiarker (srh959) homework 15 Turner...

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Unformatted text preview: hiarker (srh959) homework 15 Turner (58220) 1 This print-out should have 12 questions. Multiple-choice questions may continue on the next column or page find all choices before answering. 001 10.0 points A hot rod of mass 1400 kg, starting from rest reaches a speed of 190 m / s in only 17 . 7 s. What is the average output power? 1. 1 . 42768 MW correct 2. . 000424527 MW 3. . 0150282 MW 4. . 0806601 MW 5. 2 . 85537 MW Explanation: The average output power is equal to the kinetic energy acquired divided by the total time, so P = 1 2 mv 2 t = (1400 kg) (190 m / s) 2 2 (17 . 7 s) mW 10 6 W = 1 . 42768 MW 002 10.0 points A car with a mass of 1 . 29 10 3 kg starts from rest and accelerates to a speed of 12.4 m/s in 10.3 s. Assume that the force of resistance remains constant at 347.9 N during this time. What is the average power developed by the cars engine? Correct answer: 11785 . 6 W. Explanation: Let : m = 1 . 29 10 3 kg , v f = 12 . 4 m / s , t = 10 . 3 s , and F r = 347 . 9 N . v f = a t and x = 1 2 a ( t ) 2 since v i = 0 m/s, and F = m a + F r , so P = F x t = F 1 2 a ( t ) 2 t = F a t 2 = ( m a + F r ) v f 2 = parenleftBig m v f t + F r parenrightBig v f 2 = bracketleftbigg (1290 kg)(12 . 4 m / s) 10 . 3 s + 347 . 9 N bracketrightbigg 12 . 4 m / s 2 = 11785 . 6 W . 003 10.0 points A car weighing 8200 N moves along a level highway with a speed of 83 km / h. The power of the engine at this speed is 75 kW. The car encounters a hill inclined at an angle of 7 . 3 with respect to the horizontal....
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This note was uploaded on 04/23/2010 for the course PHY 303K taught by Professor Nui during the Spring '09 term at University of Texas-Tyler.

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HW15_Solutions - hiarker (srh959) homework 15 Turner...

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