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Unformatted text preview: homework 09 GAUTHIER, JOSEPH Due: Nov 2 2007, 1:00 am 1 Question 1, chap 12, sect 2. part 1 of 2 10 points A record has an angular speed of 38 . 3 rev / min. What is its angular speed? Correct answer: 4 . 01077 rad / s (tolerance 1 %). Explanation: 1 rev = 6 . 28319 rad, and 1 min = 60 s , Therefore, 1 = (38 . 3 rev / min) parenleftbigg 2 rad rev parenrightbiggparenleftbigg 1 min 60 s parenrightbigg = 4 . 01077 rad / s . Question 2, chap 12, sect 2. part 2 of 2 10 points Through what angle, in radians, does it rotate in 1 . 33 s? Correct answer: 5 . 33432 rad (tolerance 1 %). Explanation: = t = (4 . 01077 rad / s) (1 . 33 s) = 5 . 33432 rad . Question 3, chap 12, sect 2. part 1 of 2 10 points A racing car travels on a circular track of radius 290 m. The car moves with a constant linear speed of 39 . 8 m / s. Find its angular speed. Correct answer: 0 . 137241 rad / s (tolerance 1 %). Explanation: The linear speed v and the angular speed are related by, v = R = v R . Question 4, chap 12, sect 2. part 2 of 2 10 points Find the magnitude of its acceleration. Correct answer: 5 . 46221 m / s 2 (tolerance 1 %). Explanation: If the car is moving at a constant speed, there is no tangential acceleration, thus the acceleration is purely radial, a r = v 2 R . Question 5, chap 12, sect 2. part 1 of 1 10 points A woman passes through a revolving door with a tangential speed of 1.6 m/s. If she is 0.76 m from the center of the door, what is the doors angular speed? Correct answer: 2 . 10526 rad / s (tolerance 1 %). Explanation: Basic Concept: v t = r Given: v t = 1 . 6 m / s r = 0 . 76 m Solution: = v t r = 1 . 6 m / s . 76 m = 2 . 10526 rad / s Question 6, chap 12, sect 2. part 1 of 1 10 points The speed of a moving bullet can be deter mined by allowing the bullet to pass through two rotating paper disks mounted a distance 62 cm apart on the same axle. From the homework 09 GAUTHIER, JOSEPH Due: Nov 2 2007, 1:00 am 2 angular displacement 42 . 8 of the two bul let holes in the disks and the rotational speed 1270 rev / min of the disks, we can determine the speed v of the bullet. 42 . 8 v 1270 rpm 62 cm What is the speed of the bullet? Correct answer: 110 . 383 m / s (tolerance 1 %). Explanation: Let : = 1270 rev / min , d = 62 cm , and = 42 . 8 . From = t the time to pass through an angle is t = = (42 . 8 ) (132 . 994 rad / s) rad 180 = 0 . 0056168 s . Then the speed of the bullet is v = d t = (62 cm) (0 . 01 m / cm) . 0056168 s = 110 . 383 m / s . Question 7, chap 12, sect 2. part 1 of 3 10 points A car accelerates uniformly from rest and covers a distance of 52 m in 8 . 4 s....
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This note was uploaded on 03/19/2008 for the course M 408M taught by Professor Gilbert during the Fall '07 term at University of Texas at Austin.
 Fall '07
 Gilbert

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