Exam-F-Practice2009spring-phys172-answers

Exam-F-Practice2009spring-phys172-answers - PRACTICE FILAL...

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PRACTICE FILAL EXAM SPRING 2009, PHYS 172 (with answers) 1. Consider a system of 8 one-dimensional harmonic oscillators. Initially this system has 3 quanta of energy. By how much does the entropy change if you add one more quantum of energy? A. zero B. 1.40 x 10 -23 J/K C. 1.52 x 10 -23 J/K D. 1.21 x 10 -23 J/K E. 1.63 x 10 -23 J 2. A skater pushes straight away from a wall. She pushes on the wall with a force whose magnitude is F , so the wall pushes on her with a force F (in the direction of her motion). As she moves away from the wall, her center of mass moves a distance d . What is the correct form of the energy principle for the point particle system consisting of the skater? A. Δ K trans + Δ E internal = Fd B. Δ K trans + Δ E internal = –Fd C. Δ K trans + Δ E internal = 0 D. Δ K trans = Fd E. Δ K trans = –Fd
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3. Consider the example of Tarzan swinging on a vine. Let the length be L = 10 m, and Tarzan has a mass of M = 70 kg. The figure shows him swinging through the bottom of the arc, where at that instant he has a speed of 13.0 m/s. What is the tension in the vine? A. 686 N B. 823 N C. 1869 N D. 1153 N E. 1335 N 4. Consider the mass-spring system as shown. Assume a frictionless surface, a mass m = 4.0 kg, and spring constant k = 100 N/m. The mass is pulled to the right by a distance x=0.3 m from its equilibrium position, and is held at rest. At time t = 0, it is released. In the subsequent oscillations of the mass, what is its maximum speed? A. 1.5 m/s B. 2.5 m/s C. 1.8 m/s D. 3.5 m/s E. 1.1 m/s
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5. Consider a system initially consisting of one ice cube and one cup of hot tea. The ice cube is added to the hot tea, and after a while the ice cube has melted and the system is in equilibrium. (Ignore any heat loss to the surroundings.) Choose the physically correct statement: A. The melting is irreversible because the final state has lower energy. B. The melting is irreversible because the final state has lower entropy. C.
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This note was uploaded on 11/02/2009 for the course PHYS 172 taught by Professor ? during the Spring '08 term at Purdue University-West Lafayette.

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Exam-F-Practice2009spring-phys172-answers - PRACTICE FILAL...

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