Exam 3 - Exam 3 Physics PointsAwarded PointsMissed...

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Exam 3 – Physics Points Awarded 46.00 Points Missed 4.00 Percentage 92.0% 1. Consider four point masses: the 1.0 kg mass is 1.0 m from the origin, the 2.0 kg mass is 2.0 m from the origin, the 3.0 kg mass is 3.0 m from the origin, and the 4.0 kg mass is 4.0 m from the origin. The acceleration due to gravity is the same everywhere. What is the x coordinate of the center of gravity for this system? a. 2.0 m b. 2.7 m c. 3.0 m d. 3.3 m e. 3.8 m Response Details: The x - coordinate of the center of mass X equal to the sum of moments about y-axis ΣMy i over the sum of masses Σm i . X = ΣMy i / Σm i ΣMy i = 1x1 +2x2 + 3x3 + 4x4 = 30 m/kg Σm i = 1 + 2 + 3 + 4 = 10 kg X = ΣMy i / Σm i = 30 / 10 = 3 m 6. Consider four point masses located as shown in the sketch. The acceleration due to gravity is the same everywhere. 1kg 2kg 3kg 4kg 1m 2m 3m 4m x x 0 1 m 2 m 3 m 4 m 1 kg 2 kg 3 kg 4 kg What is the x coordinate of the center of gravity for this system? (a) 2.0 m (c) 3.0 m (e) 3.8 m (b) 2.7 m (d) 3.3 m 2. A spinning skater draws in her outstretched arms thereby reducing her moment of inertia by a factor of 2. Determine the ratio of her final kinetic energy to her initial kinetic energy. a. 0.5 b. 1 c. 2 d. 4 e. 16 http://www.esu.edu/physics/jelwood/s04161fi.htm
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10. A spinning skater draws in her outstretched arms thereby reducing her moment of inertia by a factor of 2. Determine the ratio of her final kinetic energy to her initial kinetic energy. A. B. 1 C. 2 D. 4 E. 16 3. Which one of the following statements concerning a wheel undergoing rolling motion is true? a. The angular acceleration of the wheel must be zero m/s2. b. The tangential velocity is the same for all points on the wheel. c. The linear velocity for all points on the rim of the wheel is non-zero. d. The tangential velocity is the same for all points on the rim of the wheel. e. There is no slipping at the point where the wheel touches the surface on which it is rolling. http://www.cramster.com/answers-aug-08/physics/rolling-motion-which-statement-concerning-a-wheel- undergoing-rolling_299476.aspx Response Details: Answer: There is no slipping at the point where the wheel touches the surface on which it is rolling. (A) Since the wheel is rolling, it must have a certain angular velocity. So, (A) is false. (B) The points on the top of the wheel have a higher tangential velocity than that at the bottom. So, (B) is false. (C) Same as above. (D) Same as above. 4. A bicycle wheel of radius 0.70 m is rotating at an angular speed of 6.3 rad/s as it rolls on a horizontal surface without slipping. What is the linear speed of the wheel? a. 1.4 m/s b. 28 m/s c. 0.11 m/s d. 4.4 m/s e. 9.1 m/s : = = . * . / = . / linear momentum p mv 0 70 m 6 3 rad s 4 41 m s http://www.ahsd.org/science/stroyan/hphys/CH7/rot_kin_wq/rot_kin_wq5.htm
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4. A bicycle wheel of radius 0.70 m is turning at an angular speed of 6.3 rad/s as it rolls on a horizontal surface without slipping. What is the linear speed of the wheel? A.
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This note was uploaded on 07/24/2010 for the course PHYSICS ph205 taught by Professor Brumm during the Spring '10 term at Grantham.

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Exam 3 - Exam 3 Physics PointsAwarded PointsMissed...

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