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: ->->->->->->->->->->->-> : the min tension is 0N and the max tension is 3N. The average tension would therefore be 1.5N.
• How much work is required to stretch the rubber band from 8 cm to 10 cm?
answer/question/discussion: ->->->->->->->->->->->-> :
Work=force*distance so the W would be 1.5N(.02m) or .03 Nm.
• During the stretching process is the tension force in the direction of motion or opposite to the direction of motion?
answer/question/discussion: ->->->->->->->->->->->-> : I would think that the force is opposite to the direction of motion and the stretching force would be in the direction of motion. However tension can also act on an object hanging from a rope in which the force would be in the direction of motion, right? Both of these reasonings seem to make sense to me which is accurate?
the tension force exerted by the rubber band tends to shorten it, so that the tension exerted on an object which is stretching the band will be in the direction opposite motion
• Does the tension force therefore do positive or negative work?
answer/question/discussion: ->->->->->->->->->->->-> : Tension does negative work. The work done to the system is positive work and that is what is inflicting the tension so tension acts as almost a reciprocal as negative work.
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: ->->->->->->->->->->->-> : The work required to stretch the rubber band was .03Nm and since it is conservative, it wouldn’t change I feel that the new work would also be .03 Nm. Is this correct reasoning? PE=m*h*force could we use this also?
• 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=.5m(v^2) I am not sure how to solve this question. We need to know velocity or we could calculate potential energy above, and convert it to KE. I understand these relationships but I am a bit lost as to how to approach solving it fully.
.5(.02kg)(velocity) We need to find velocity which would be
• At this point how fast will the domino be moving?
answer/question/discussion: ->->->->->->->->->->->-> :
Again I am not sure how to solve this problem. I am assuming we needed to solve for KE and then find V using that equation. I am assuming this means my problem stems back to the PE issue. I am not sure what number to use for force.
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20 mins
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You're doing well and asking the right questions. See my note(s) above and the commentary in the link below. If you have additional questions insert them as indicated below and I'll be glad to answer.
&#Please compare your solutions with the expanded discussion at the link
Solution
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