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Rec09_172Fall11_rl

# Rec09_172Fall11_rl - m 1-m 2-spring system change How much...

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Physics 172 – Recitation 09 Fall 2011 Purpose: The purpose of this recitation is to allow you to gain further experience working with the Energy Principle as applied to internal energy. Readings: Sections 7.5-7.10 General Instructions: Identify your system State which objects are interacting with the system State the fundamental principle(s) you use to solve the problems Draw an appropriate diagram labeling key features of the problem State the approximations and simplifying assumptions you use. Problem 1. You hold a mass m 1 in your left hand and a mass m 2 in your right hand, both at rest and the same height above the floor. The masses are connected by a light spring with stiffness k . Initially, your hands are positioned so that the spring is relaxed. Later, you’ve moved your right hand horizontally a distance s closer to your left hand and are, again, holding the masses at rest. a) How much did the internal energy of the
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Unformatted text preview: m 1-m 2-spring system change? How much work did you do with your left hand on the m 1-m 2-spring system? With your right hand? Checkpoint 1 b) How much work did you do with your left hand on the m 2-only system? With your right hand? How much did the internal energy of the m 2-only system change? Did any other object in the surroundings of the m 2-only system do work on it? If so, how much? Checkpoint 2 c) It took you 5 seconds to move your right hand slowly from its initial to its final position. How does the change in momentum between the initial and final state you imparted to the m 1-m 2-spring system with your left hand compare to the change in momentum you imparted to it with your right hand? d) Compare the quantity, ! U spring , to the work done on mass 2 by the spring as mass 2 is moved from its initial position to its final position? Checkpoint 3...
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