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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: ->->->->->->->->->->->-> : The minimum tension is probably a fraction of a Newton, since it is the point at which any tension is present. The maximum is 3, Newtons, since this is the tension when the band is stretched farthest. I think the average is about 1.5, since the minimum tension is close to zero and the maximum is 3 ((0 + 3) / 2 = 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: ->->->->->->->->->->->-> :
W = F * ds = 1.5 Newtons * 0.02 m = 0.03 Joules
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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: ->->->->->->->->->->->-> :
It is opposite, since the band doesnt want to be pulled in the direction it is being pulled and will snap back if you stop pulling.
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Does the tension force therefore do positive or negative work?
answer/question/discussion: ->->->->->->->->->->->-> :
It does negative work, since it is forcing you to exert more effort to stretch it.
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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: ->->->->->->->->->->->-> : W = f * ds = 1.5 Newtons * -0.02 m = -0.03 Joules
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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 = Joules = -0.03 Joules
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At this point how fast will the domino be moving?
answer/question/discussion: ->->->->->->->->->->->-> : V = KE / (1/2 * DS) = 0.03 J / (1/2 * 0.02) = 3
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Good up to this point.
However your solution lacks units. You haven't quite solved the equation correctly; the units would tell you that and also would likely give you a good idea what step you missed.
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