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Unformatted text preview: Version 067/ABAAD – midterm 02 – Turner – (58120) 1 This printout should have 19 questions. Multiplechoice questions may continue on the next column or page – find all choices before answering. 001 10.0 points It takes 5 . 69 J of work to stretch a Hooke’slaw spring 13 . 1 cm from its unstressed length. How much the extra work is required to stretch it an additional 8 . 85 cm? 1. 27.5923 2. 23.9957 3. 14.6557 4. 16.0922 5. 23.5887 6. 8.09129 7. 10.1025 8. 10.2849 9. 7.14472 10. 7.31815 Correct answer: 10 . 2849 J. Explanation: We begin by determining the value of k from the energy equation solved for k , k = 2 U x 2 = 2(5 . 69 J) (0 . 131 m) 2 = 663 . 132 J / m 2 We can now determine the energy at the ad ditional displacement, U add = 1 2 k x 2 add = 1 2 663 . 132 J / m 2 (0 . 131 m + 0 . 0885 m) 2 = 15 . 9749 J The extra work required is just the difference in energy between the two displacements. W = Δ U = U add − U = 15 . 9749 J − 5 . 69 J = 10 . 2849 J 002 10.0 points How long would our year be if our Sun were one fourth its present mass and the radius of the Earth’s orbit were five times its present value? 1. 35.3553 2. 50.0 3. 18.0 4. 34.8569 5. 22.3607 6. 5.80948 7. 16.9706 8. 3.4641 9. 26.1916 10. 44.7214 Correct answer: 22 . 3607 y. Explanation: Let : M new = 1 4 M and R new = 5 R. The speed of the Earth is v = 2 π R T = radicalbigg GM R GM R = 4 π 2 R 2 T 2 T 2 = 4 π 2 R 3 Gm T = radicalbigg 4 π 2 R 3 GM ∝ radicalbigg R 3 M , so that T new T = radicalbig R 3 new M radicalbig R 3 M new = radicaltp radicalvertex radicalvertex radicalvertex radicalbt (5 R ) 3 M R 3 parenleftbigg 1 4 M parenrightbigg = √ 500 = 22 . 3607 T new = 22 . 3607 T = 22 . 3607 years . 003 10.0 points When an object is moved from rest at point A to rest at point B in a gravitational field, the net work done by the field depends on the mass of the object and 1. the velocity of the object as it moves between A and B . Version 067/ABAAD – midterm 02 – Turner – (58120) 2 2. the nature of the external force moving the object from A to B . 3. the path taken between A and B only. 4. the positions of A and B only. correct 5. both the positions of A and B and the path taken between them. Explanation: Gravitational force is a conservative force, so in addition to the mass, only the positions are needed. 004 10.0 points A curve of radius 50 . 6 m is banked so that a car traveling with uniform speed 57 km / hr can round the curve without relying on fric tion to keep it from slipping to its left or right. The acceleration of gravity is 9 . 8 m / s 2 . 2 . 8 M g μ ≈ θ What is θ ? 1. 29.1597 2. 34.7401 3. 25.0761 4. 26.8191 5. 27.6171 6. 30.9911 7. 21.7496 8. 32.0817 9. 25.8513 10. 22.4695 Correct answer: 26 . 8191 ◦ ....
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This note was uploaded on 06/14/2011 for the course PHY 303K taught by Professor Turner during the Spring '08 term at University of Texas.
 Spring '08
 Turner
 Physics, Work

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