MasteringPhysics6a - MasteringPhysics: Assignment Print View

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MasteringPhysics: Assignment Print View .. 1 of 12 10/4/2007 3:56 PM [ Print View ] PHCC 141: Physics for Scientists and Engineers I - Fall 2007 6a. Work, Energy, and Power Due at 11:59pm on Thursday, September 27, 2007 Hide Grading Details Number of answer attempts per question is: 5 You gain credit for: correctly answering a question in a Part, or correctly answering a question in a Hint. You lose credit for: exhausting all attempts or requesting the answer to a question in a Part or Hint, or incorrectly answering a question in a Part. Late submissions: reduce your score by 100% over each day late. Hints are helpful clues or simpler questions that guide you to the answer. Hints are not available for all questions. There is no penalty for leaving questions in Hints unanswered. Grading of Incorrect Answers For Multiple-Choice or True/False questions, you lose 100% / ( # of options - 1 ) credit per incorrect answer. For any other question, you lose 3% credit per incorrect answer. Work Energy Theorem and Exercises The Work-Energy Theorem Learning Goal: To understand the meaning and possible applications of the work-energy theorem. In this problem, you will use your prior knowledge to derive one of the most important relationships in mechanics: the work-energy theorem. We will start with a special case: a particle of mass moving in the x direction at constant acceleration . During a certain interval of time, the particle accelerates from to , undergoing displacement given by . Part A Find the acceleration of the particle. Hint A.1 Some helpful relationships from kinematics By definition, . Furthermore, the average speed is , and the displacement is . Combine these relationships to eliminate . Express the acceleration in terms of , , and . ANSWER: = Part B Find the net force acting on the particle. Hint B.1 Using Newton's laws Hint not displayed Express your answer in terms of and . ANSWER: = Part C
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MasteringPhysics: Assignment Print View .. 2 of 12 10/4/2007 3:56 PM Find the net work done on the particle by the external forces during the particle's motion. Express your answer in terms of and . ANSWER: = Part D Substitute for from Part B in the expression for work from Part C. Then substitute for from the relation in Part A. This will yield an expression for the net work done on the particle by the external forces during the particle's motion in terms of mass and the initial and final velocities. Give an expression for the work in terms of those quantities. Express your answer in terms of , , and . ANSWER: = The expression that you obtained can be rearranged as The quantity has the same units as work. It is called the kinetic energy of the moving particle and is denoted by . Therefore, we can write
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