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MP #8 - Print View Class PH1110A2007 Assignment 8 Due at...

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1 of 10 [ Print View ] Class PH1110A2007 Assignment 8 Due at 5:00pm on Monday, September 17, 2007 View Grading Details All Work and No Play Learning Goal: To be able to calculate work done by a constant force directed at different angles relative to displacement If an object undergoes displacement while being acted upon by a force (or several forces), it is said that work is being done on the object. If the object is moving in a straight line and the displacement and the force are known, the work done by the force can be calculated as , where is the work done by force on the object that undergoes displacement directed at angle relative to . Note that depending on the value of , the work done can be positive, negative, or zero. In this problem, you will practice calculating work done on an object moving in a straight line. The first series of questions is related to the accompanying figure. Part A What can be said about the sign of the work done by the force ? ANSWER: It is positive. It is negative. It is zero. There is not enough information to answer the question. When , the cosine of is zero, and therefore the work done is zero. Part B What can be said about the work done by force ? ANSWER: It is positive.
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2 of 10 It is negative. It is zero. When , is positive, and so the work done is positive. Part C The work done by force is ANSWER: positive negative zero When , is negative, and so the work done is negative. Part D The work done by force is ANSWER: positive negative zero Part E The work done by force is ANSWER: positive negative zero Part F The work done by force is ANSWER: positive negative zero Part G The work done by force is ANSWER: positive negative zero In the next series of questions, you will use the formula to calculate the work done by various forces on an object that moves 160 meters to the right.
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3 of 10 Part H Find the work done by the 18-newton force. Use two significant figures in your answer. Express your answer in joules. ANSWER: = 2900 Part I Find the work done by the 30-newton force. Use two significant figures in your answer. Express your answer in joules. ANSWER: = 4200 Part J Find the work done by the 12-newton force. Use two significant figures in your answer. Express your answer in joules. ANSWER: = -1900 Part K Find the work done by the 15-newton force. Use two significant figures in your answer. Express your answer in joules. ANSWER: = -1800 Understanding Work and Kinetic Energy Learning Goal: To learn about the Work-Energy Theorem and its basic applications. In this problem, you will learn about the relationship between the work done on an object and the kinetic energy of that object. The kinetic energy of an object of mass moving at a speed is defined as . It seems reasonable to say that the speed of an object--and, therefore, its kinetic energy--can be changed by performing work on the object. In this problem, we will explore the mathematical relationship between the work done on an object and the change in the kinetic energy of that object.
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