Assignment #5 Reading, Objectives, & Problems
A. Availability and Due Dates
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Assignment #5 is available Thursday, October 20, 2004. The target date for its successful completion is Thursday, October 27, 2004. In any event, all of the Type A problems from Assignment #5 must be successfully completed and turned in by 5:00 pm on Friday, November 5, 2004. If this requirement is not met, the student will not be allowed to take Quiz 3, to be given in class on Tuesday, November 9, 2004. |
B. Reading
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As preparation for completing the problems in Assignment #5, read Chapters 10 & 11 in Cohen's The Fundamentals of College Physics, Volume IB. |
C. Objectives
In addition to the Objectives listed on Assignments 1- 4, after completing Assignment #5, the student should
[1] Be able to analyze the motion of objects in situations in which the net force acting on the objects is proportional to time. Specifically, the student should realize that this results in a non-constant acceleration, and therefore prevents one from using constant acceleration formulae.
[2] Be able to determine the average acceleration of an object in a situation in which the force acting upon it is proportional to time. The student should then be able to use this information to determine the object's velocity as a function of time.
[3] Be able to analyze the motion of objects in situations in which the net force acting on the objects is proportional to distance. As in Objective [1] above, the student should realize that this results in a non-constant acceleration, and therefore prevents one from using constant acceleration formulae.
[4] Be able to determine the distance-averaged acceleration of an object in a situation in which the force acting upon it is proportional to distance. The student should then be able to use this information to determine the object's velocity as a function of distance.
[5] Be able to explain the difference between time-averaged and distance-averaged quantities.
[6] Be able to analyze arbitrary problems in which the acceleration of an object is "piece-wise constant". In this sense, "piece-wise constant" refers to motion that can be broken up into a set of intervals during each of which the object undergoes constant acceleration.
[7] Know the definition of work, and be able to calculate the work done on an object by an arbitrary collection of forces. In particular, the student should realize that no work is done on an object unless the object moves in a direction parallel to the direction of the net force.
[8] Know the definition of Kinetic Energy. In particular, the student should realize that kinetic energy is energy associated with motion: an object at rest has no kinetic energy.
[9] Know that the unit Joule is a measure of energy. Know that 1 Joule is the same as
1 kg·m2/s2 , or, equivalently, the same as 1 N·m.
[10] Be able to use the concepts of work and kinetic energy to determine the motion of objects in arbitrary situations in which the forces acting are known.
D. Type A Problems
[1] Suppose that an object of mass 20 kg is initially at rest. At time t = 0, a force whose strength is proportional to time begins to act upon the object:
How long does it take for the object to reach a speed of 160 m/s ?
[2] Problem 11.1 on p. 261 of Cohen.
[3] Problem 11.2 on pp. 261-262 of Cohen.
[4] Problem 11.3 on p. 262 of Cohen.
[5] A ball of mass m is attached to the end of a string of length 41 cm in order to create a pendulum. As the pendulum swings back and forth, it is noted that the horizontal speed of the pendulum as it passes through its lowest point is 1.5 m/s. To what maximum angle does the pendulum swing?
E. Type B Problems
[6] A block of mass 55 kg slides down the decline shown below. The length of the sloped surface of the decline is 15 meters.
SHAPE \* MERGEFORMAT
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Assuming that the decline is frictionless, determine the total work done by gravity on the block as it slides down the decline. |
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Assuming that there is a coefficient of kinetic friction of ìk = 0.1 between the block and the decline, determine the total work done by friction on the block as it slides down the decline. |
[7] An object of mass 500 grams is attached to the end of a spring. As a result, it experiences a force given by the expression:
Note that, when the mass is at the origin, it experiences no force.
Suppose that the object is pulled 10 cm to the right of the origin, and is then released from rest. Determine the speed of the object as it passes through the origin.