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Phy 201
Your 'cq_1_15.1' 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?
answer/question/discussion: ->->->->->->->->->->->-> :
The minimum tension would be 0 N and the max would be 3 N.
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• Assuming that the tension in the rubber band is 100% conservative (which is not actually the case) what is its elastic potential energy at the 10 cm length?
answer/question/discussion: ->->->->->->->->->->->-> :
3N* 10cm= 30 J
3 N is the maximum force, not the average force
The force is not exerted through 10 cm. The rubber band exerts no force when its length is less than 8 cm.
Also note that N * cm is not J. A Joule is a Newton * meter.
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• If all this potential energy is transferred to the kinetic energy of an initially stationary 20 gram domino, what will be the velocity of the domino?
answer/question/discussion: ->->->->->->->->->->->-> :
We will use the formula: KE= ½ m v^2
30J= ½ (20g) (v^2)
30J=10 (v^2)
3= v^2
1.7cm/s= v
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• If instead the rubber band is used to 'shoot' the domino straight upward, then how high will it rise?
answer/question/discussion: ->->->->->->->->->->->-> :
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30J= 3N*’ds
10cm=’ds
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10 minutes
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