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course phy 201
I'm sure around the end those are wrong I just don't feel its right
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:
at 8 it is zero at ten it is 3
Average is 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:
3 * 2 = 6 joules
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Your quantities and your final result have units, which always need to be included.
3 N is the maximum force. As the rubber band shortens its tension decreases, so the 3 N force is exerted only for an instant. The result of your calculation would therefore overestimate the work.
The final units of this calculation would not be 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:
In the direction opposite of motion
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Does the tension force therefore do positive or negative work?
answer/question/discussion:
Negative
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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:
I would guess 6 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:
6 joules
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At this point how fast will the domino be moving?
answer/question/discussion:
assuming the dominoes mass is 1 gram
.5 * .001 * v^2 = 6
109 m /s
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Self-critique (if necessary):
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Self-critique rating:
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If a 1 gram mass was moving at 109 m/s, it would have an energy of 6 Joules. So you're setting the right expression equal to the energy and solving the equation correctly.
Domino mass was given and should be used in this calculation.
Your calculation of energy did not use units correctly so you got a result that's off by more than one order of magnitude. You also did not use an appropriate force to find the energy.
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