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PHY 201
Your 'cq_1_14.1' report has been received. Scroll down through the document to see any comments I might have inserted, and my final comment at the end.
** CQ_1_14.1_labelMessages **
A rubber band begins exerting a tension force when its length is 8 cm. As it is stretched to a length of 10 cm its tension increases with length, more or less steadily, until at the 10 cm length the tension is 3 Newtons.
•Between the 8 cm and 10 cm length, what are the minimum and maximum tensions, and what do you think is the average tension?
answer/question/discussion: ->->->->->->->->->->->-> :
At 10 cm in length occurs the maximum tension of 3 Newtons. I do not know how to calculate tension, but I know at 8 cm in length, occurs the minimum tension ( which might be 0 Newtons ), notwithstanding the instance where the rubber band is undisturbed. I am guessing 2.4 Newtons, using the law of proportions ( 3 * 8 /10 ). I would think you would have to know the rubber band's initial length in order to find its real point of lowest tension force or its acceleration. Thus, I believe the average tension is 2.7 Newtons between this interval of lengths.
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The situation is simpler than that.
The tension at length 8 cm is 0, the tension at length 10 cm is 3 N.
So the average tension, assuming that tension changes linearly with length, would be halfway between the minimum and the maximum, or 1.5 Newtons.
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•How much work is required to stretch the rubber band from 8 cm to 10 cm?
answer/question/discussion: ->->->->->->->->->->->-> :
To stretch the rubber band the rubber band 2 cm, it takes .06 J or .06 N-m ( .02 m * 3 Newtons ).
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•During the stretching process is the tension force in the direction of motion or opposite to the direction of motion?
answer/question/discussion: ->->->->->->->->->->->-> :
During the stretching process, the tension force I believe is in the opposite direction of motion, once past its modulus of elasticity because the rubber band by nature experience less stress and strain at rest. Before that point at which it exceeds its yield strength, I think the stretching process is moving in the direction of motion. Thus, anything past that point, would be in the direction opposite of motion.
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•Does the tension force therefore do positive or negative work?
answer/question/discussion: ->->->->->->->->->->->-> :
Negative
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The rubber band is released and as it contracts back to its 8 cm length it exerts its tension force on a domino of mass .02 kg, which is initially at rest.
•Again assuming that the tension force is conservative, how much work does the tension force do on the domino?
answer/question/discussion: ->->->->->->->->->->->-> :
the tension force is .01568 N-m or .01568 Joules ( .02 kg * 9.8 m/s^2 * .08 m ).
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•Assuming this is the only force acting on the domino, what will then be its kinetic energy when the rubber band reaches its 8 cm length?
answer/question/discussion: ->->->->->->->->->->->-> :
KE = 1/2( .02 kg )(( .392 m/s)^2)
= .00153664 kg m^2/s^2
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•At this point how fast will the domino be moving?
answer/question/discussion: ->->->->->->->->->->->-> :
vf = 'sqrt.( 2 * .03 Joules / ( .02 kg ))
vf = 'sqrt( 3 m^2/s^2 )
vf = 1.73 m/s ( est. )
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30 min
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