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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.
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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: ->->->->->->->->->->->-> :
Minimum would be 0N.
Maximum would be 3N.
Average would be 3N/2=1.5N.
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How much work is required to stretch the rubber band
from 8 cm to 10 cm?
answer/question/discussion: ->->->->->->->->->->->-> :
F*'ds,
3kg*m/s^2*.02m=.06kg*m^2/s^2 or .06 Joules
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@& The work done is the average force * distance, not maximum force * distance.
You just found the correct average force.*@
During the stretching process is the tension force in
the direction of motion or opposite to the direction
of motion?
answer/question/discussion: ->->->->->->->->->->->-> :
Opposite the direction of motion.
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Does the tension force therefore do positive or
negative work?
answer/question/discussion: ->->->->->->->->->->->-> :
Negative work.
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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: ->->->->->->->->->->->-> :
F=ma
F=.02kg*9.8m/s^2
F=.19N
-3N+.19N=-2.81N
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@& Gravity is not involved in this situation. So 9.8 m/s^2 is not relevant.
The force here is the force exerted by the elastic object.*@
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: ->->->->->->->->->->->-> :
2.81N/.02kg=140.5m/s^2
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At this point how fast will the domino be moving?
answer/question/discussion: ->->->->->->->->->->->-> :
vf^2=v0^2+(2*a*'ds),
vf=sqrt(2*140.5m/s^2*.02m),
vf=sqrt(5.62m^2/s^2),
vf=2.4m/s approximate
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*#&!
@& You went off track when you invoked gravity.
&#See any notes I might have inserted into your document, and before looking at the link below see if you can modify your solutions. If there are no notes, this does not mean that your solution is completely correct.
Then please compare your old and new solutions with the expanded discussion at the link
Solution
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