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Unformatted text preview: homework 09 BROWNING, ADAM 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 52 . 3 rev / min. What is its angular speed? Correct answer: 5 . 47685 rad / s (tolerance 1 %). Explanation: 1 rev = 6 . 28319 rad, and 1 min = 60 s , Therefore, 1 = (52 . 3 rev / min) parenleftbigg 2 rad rev parenrightbiggparenleftbigg 1 min 60 s parenrightbigg = 5 . 47685 rad / s . Question 2, chap 12, sect 2. part 2 of 2 10 points Through what angle, in radians, does it rotate in 0 . 727 s? Correct answer: 3 . 98167 rad (tolerance 1 %). Explanation: = t = (5 . 47685 rad / s) (0 . 727 s) = 3 . 98167 rad . Question 3, chap 12, sect 2. part 1 of 2 10 points A racing car travels on a circular track of radius 397 m. The car moves with a constant linear speed of 21 . 8 m / s. Find its angular speed. Correct answer: 0 . 0549118 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: 1 . 19708 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 2.0 m/s. If she is 0.63 m from the center of the door, what is the doors angular speed? Correct answer: 3 . 1746 rad / s (tolerance 1 %). Explanation: Basic Concept: v t = r Given: v t = 2 . 0 m / s r = 0 . 63 m Solution: = v t r = 2 m / s . 63 m = 3 . 1746 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 78 . 2 cm apart on the same axle. From the homework 09 BROWNING, ADAM Due: Nov 2 2007, 1:00 am 2 angular displacement 24 . 5 of the two bul let holes in the disks and the rotational speed 1410 rev / min of the disks, we can determine the speed v of the bullet. 24 . 5 v 1410 rpm 78 . 2 cm What is the speed of the bullet? Correct answer: 270 . 029 m / s (tolerance 1 %). Explanation: Let : = 1410 rev / min , d = 78 . 2 cm , and = 24 . 5 . From = t the time to pass through an angle is t = = (24 . 5 ) (147 . 655 rad / s) rad 180 = 0 . 00289598 s . Then the speed of the bullet is v = d t = (78 . 2 cm) (0 . 01 m / cm) . 00289598 s = 270 . 029 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 64 m in 8 . 9 s....
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This note was uploaded on 02/24/2010 for the course PHY 303K taught by Professor Turner during the Fall '08 term at University of Texas at Austin.
 Fall '08
 Turner
 Physics, Work

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