Physics Test3 Solutions - quiz 03 – VENNES, ROSS – Due:...

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Unformatted text preview: quiz 03 – VENNES, ROSS – Due: Nov 14 2007, 10:00 pm 1 Question 1, chap 9, sect 1. part 1 of 1 10 points Given: G = 6 . 673 × 10 − 11 N m 2 / kg 2 Two balls, each with a mass of 0.885 kg, exert a gravitational force of 8 . 30 × 10 − 11 N on each other. How far apart are the balls? 1. . 66031 m 2. . 6809 m 3. . 702014 m 4. . 723889 m 5. . 746456 m 6. . 769596 m 7. . 793533 m correct Explanation: Basic Concept: F g = G m 1 m 2 r 2 Given: m 1 = m 2 = 0 . 885 kg F g = 8 . 30 × 10 − 11 N G = 6 . 673 × 10 − 11 N · m 2 kg 2 Solution: r 2 = Gm 1 m 2 F g = parenleftBig 6 . 673 × 10 − 11 N · m 2 kg 2 parenrightBig (0 . 885 kg) 2 8 . 3 × 10 − 11 N = 0 . 629694 m 2 Thus r = √ . 629694 m 2 = 0 . 793533 m Question 2, chap 12, sect 5. part 1 of 2 10 points A wheel is formed from a hoop and four equally spaced spokes. The hoop’s radius is the length of each spoke. . 062 kg 1 . 7 kg . 71 m There are four equally spaced spokes. Each spoke has mass 0 . 062 kg. The hoop’s mass is 1 . 7 kg. The hoop’s radius is 0 . 71 m. Determine the moment of inertia of the wheel about an axis through its center and perpendicular to the plane of the wheel. 1. . 898642 kg m 2 correct 2. . 928128 kg m 2 3. . 957917 kg m 2 4. . 988384 kg m 2 5. 1 . 0235 kg m 2 6. 1 . 05601 kg m 2 7. 1 . 09156 kg m 2 8. 1 . 12826 kg m 2 9. 1 . 16531 kg m 2 10. 1 . 22513 kg m 2 Explanation: Let : n = 4 spokes , m = 0 . 062 kg , M = 1 . 7 kg , and R = 0 . 71 m . Each spoke contributes to the total moment of inertia as a thin rod pivoted at one end, hence I = M R 2 + n mR 2 3 = bracketleftBig M + n m 3 bracketrightBig R 2 = bracketleftbigg (1 . 7 kg) + 4 (0 . 062 kg) 3 bracketrightbigg (0 . 71 m) 2 = 0 . 898642 kg m 2 . Question 3, chap 12, sect 5. part 2 of 2 10 points quiz 03 – VENNES, ROSS – Due: Nov 14 2007, 10:00 pm 2 Determine the moment of inertia of the wheel about an axis through its rim and per- pendicular to the plane of the wheel. 1. 1 . 53732 kg m 2 2. 1 . 58682 kg m 2 3. 1 . 63821 kg m 2 4. 1 . 69714 kg m 2 5. 1 . 75496 kg m 2 6. 1 . 81539 kg m 2 7. 1 . 88063 kg m 2 correct 8. 1 . 94568 kg m 2 9. 2 . 01144 kg m 2 10. 2 . 07368 kg m 2 Explanation: From the parallel axis theorem I rim = I + ( M + n m ) R 2 = (0 . 898642 kg m 2 ) + [(1 . 7 kg) + 4 (0 . 062 kg)] (0 . 71 m) 2 = 1 . 88063 kg m 2 . Question 4, chap 10, sect 2. part 1 of 1 10 points Pat builds a track for his model car out of wood. The track is 4 cm wide (along the z coordinate), 1 m high (along the y coordi- nate) and 3 . 4 m long (along the x coordinate starting from x = 0). The runway is cut such that it forms part of the left-hand side of a parabola, see figure below. x 1m y 3 . 4 m y = 1 (11 . 56 m) [ x − (3 . 4 m)] 2 4 cm Locate the horizontal position of the center of gravity of this track....
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This homework help was uploaded on 04/18/2008 for the course PHY 303K taught by Professor Turner during the Spring '08 term at University of Texas at Austin.

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Physics Test3 Solutions - quiz 03 – VENNES, ROSS – Due:...

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