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Unformatted text preview: lenoir (wml297) – homework 15 – Turner – (58220) 1 This printout should have 12 questions. Multiplechoice questions may continue on the next column or page – find all choices before answering. 001 10.0 points A car with mass 854 kg passes over a bump in a road that follows the arc of a circle of radius 57 . 6 m as shown in the figure. The acceleration of gravity is 9 . 8 m / s 2 . 5 7 . 6 m v 854 kg What is the maximum speed the car can have as it passes the highest point of the bump before losing contact with the road? Correct answer: 23 . 8 m / s. Explanation: At the highest point, we have mg N = mv 2 r , where N is the normal force. To get the maximum speed, we need N = 0 . Therefore, v max = √ g r = radicalBig (9 . 8 m / s 2 ) (57 . 6 m) = 23 . 8 m / s . 002 (part 1 of 2) 10.0 points A small sphere of mass m is connected to the end of a cord of length r and rotates in a vertical circle about a fixed point O. The tension force exerted by the cord on the sphere is denoted by T . r O θ What is the correct equation for the forces in the radial direction when the cord makes an angle θ with the vertical? 1. T mg sin θ = mv 2 r tan θ 2. T mg sin θ = + mv 2 r cos θ 3. T mg sin θ = + mv 2 r 4. T mg sin θ = + mv 2 r tan θ 5. T + mg cos θ = + mv 2 r 6. T mg sin θ = mv 2 r 7. T + mg sin θ = + mv 2 r 8. None of these 9. T mg cos θ = + mv 2 r correct Explanation: O θ θ mg T The centripetal force is F c = mv 2 r . This centripetal force is provided by the ten sion force and the radial component of the weight. In this case, they are in opposite lenoir (wml297) – homework 15 – Turner – (58220) 2 direction, so F c = mv 2 r = T mg cos θ . 003 (part 2 of 2) 10.0 points What is the magnitude of the total accel eration? You may want to first find both the radial and the tangential component of the acceleration. 1.  vectora  = radicalBigg parenleftbigg T m parenrightbigg 2 + g 2 cos 2 θ 2.  vectora  = radicalBigg parenleftbigg T m parenrightbigg 2 + g 2 3.  vectora  = radicalBigg parenleftbigg T m parenrightbigg 2 g 2 4.  vectora  = radicalBigg parenleftbigg T m parenrightbigg 2 sin 2 θ + g 2 cos 2 θ 5. None of these 6.  vectora  = radicalBigg parenleftbigg T m parenrightbigg...
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This note was uploaded on 04/15/2010 for the course PHY 12343 taught by Professor Turner during the Spring '10 term at University of Texas.
 Spring '10
 Turner

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