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Phy 121
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.
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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: ->->->->->->->->->->->-> :
Min. 0 N
Max. 3 N
3 N / 2 = 1.5 N avg. tension
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• How much work is required to stretch the rubber band from 8 cm to 10 cm?
answer/question/discussion: ->->->->->->->->->->->-> :
3 N because that is what it takes to store the KE in the tension.
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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: ->->->->->->->->->->->-> :
As you pull out the tension wants to pull it in, so I would say the tension force is opposite the direction of the motion, which allows it to store KE.
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• Does the tension force therefore do positive or negative work?
answer/question/discussion: ->->->->->->->->->->->-> :
I think you could say it is either depending upon which direction you are implying is positive.
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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: ->->->->->->->->->->->-> :
3 N * .02 Kg = .06 N tension force on the domino
@& You need to multiply the average tension by the displacement.
3 N is the maximum tension.
The displacement is .02 m rather than .02 kg, but that's just a typo on your part.*@
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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: ->->->->->->->->->->->-> :
since at 8 cm it is at its minimum tension force, 0 N the KE would be 0 as well.
@& The domino has been accelerated during the entire interval, so it's got some KE. The acceleration is decreasing along with the tension, but the tension force has done its work.*@
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• At this point how fast will the domino be moving?
answer/question/discussion: ->->->->->->->->->->->-> :
.06 N / .02 kg = 3 m/s
???
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*#&!*#&!
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Then please compare your old and new solutions with the expanded discussion at the link
Solution
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