phy201
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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Seed question 14
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 - 3 newtons the max is + 3 newtons
In think that the average tension would be 3/2 = 1.5
#$&*
How much work is required to stretch the rubber band from 8 cm to 10 cm?
answer/question/discussion: ->->->->->->->->->->->-> :
'dw= F * 'ds
'dw = 3newtons * 10cm
'dw= 30joules
N * cm is not Joules; N * m is Joules. You need a conversion here.
`dW = F_ave * `ds. The average force isn't 3 Joules.
#$&*
During the stretching process is the tension force in the direction of motion or opposite to the direction of motion?
answer/question/discussion: ->->->->->->->->->->->-> :
I think tension is the force that is opposing the direction of motion. As the band stretches the tension is what causes it to slow down.
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Does the tension force therefore do positive or negative work?
answer/question/discussion: ->->->->->->->->->->->-> :
Tension force does positive work on the systme in the opposite direction
tension force opposes motion. Therefore whichever is positive, tension or displacement, the other is negative and F * `ds gives you a negative result.
#$&*
The rubber band is released and as it contracts back to its 8 cm length it exerts its tension force on a domino of mass .02 kg, which is
initially at rest.
Again assuming that the tension force is conservative, how much work does the tension force do on the domino?
answer/question/discussion: ->->->->->->->->->->->-> :
#$&*
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: ->->->->->->->->->->->-> :
F= m * a
F= .02kg * 9.8m/s^2
F= .196 newtons
Dw= fnet * ds
dw= .196 * .08meters
'dw= .016J
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At this point how fast will the domino be moving?
answer/question/discussion: ->->->->->->->->->->->-> :
F= m *a
a = m/f
a= .02kg/.196 newtons
a= .102 m/s^2
#$&*
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about 30 minutes
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&#Please compare your solutions with the expanded discussion at the link
Solution
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