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Phy 231
Your 'cq_1_16.1' 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 has no tension until it reaches a length of 7.5 cm. Beyond that length its tension increases by .7 Newtons for every additional centimeter of length.
What will be its tension if its endpoints are at the points (5 cm, 9 cm) and (10 cm, 17 cm) as measured on an x-y coordinate system?
answer/question/discussion: ->->->->->->->->->->->-> :
d= sq((10cm - 5cm) + (17cm - 9cm))= 9.4cm
9.4cm - 7.5cm= 1.9cm/.7= 2.7N
@& I don't have any trouble understanding your intent, but you will find it less likely to cause confusion for readers (including yourself if you review your work at a later date) if you avoid using = signs for train of thought.
9.4cm - 7.5cm= 1.9cm/.7= 2.7N
is not a true statement Is says that
9.4cm - 7.5cm= 2.7N,
which is clearly false.
You would have been better off to write this as
9.4cm - 7.5cm= 1.9cm
1.9 cm / .7= 2.7N.
This is still not true. 1.9 cm / .7 = 2.7 cm, not 2.7 N.
Using units you would have
1.9 cm / (.7 N / cm) = 2.7 cm^2 / N,
which is also clearly flawed because of the units.
However this would likely lead you to reconsider your calculation, and it would then be likely that you would get the right result.*@
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What is the vector from the first point to the second?
answer/question/discussion: ->->->->->->->->->->->-> :
(5cm, 8cm) ?
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What is the magnitude of this vector?
answer/question/discussion: ->->->->->->->->->->->-> :
9.4
@& 9.4 cm*@
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What vector do you get when you divide this vector by its magnitude? (Specify the x and y components of the resulting vector).
answer/question/discussion: ->->->->->->->->->->->-> :
??? I dont understand what quantities am I dividing with. . . v/9.4?
@& The vector is <5 cm, 8 cm>.
You will divide this vector by its 9.4 cm magnitude.*@
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The new vector should have magnitude 1. When you divide a vector by its magnitude the result is a vector with magnitude 1. We call a vector of magnitude 1 a unit vector. What vector do you get when you multiply this new vector (i.e., the unit vector) by the tension?
answer/question/discussion: ->->->->->->->->->->->-> :
?????
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What are the x and y components of the new vector?
answer/question/discussion: ->->->->->->->->->->->-> :
???? as you can see, I need help with vectors
@& The vector calculation is actually pretty straightforward, but if you're not experienced with vectors the meaning and interpretation of your results will give you trouble. I'll append a longer discussion of this problem.*@
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This new vector is called the tension vector. It is a force vector which represents the tension. A force vector can be specified by its components, or equivalently by its magnitude and direction.
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45min
@&
&#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
Self-critique your solutions, if this is necessary, according to the usual criteria. Insert any revisions, questions, etc. into a copy of this posted document. Mark any insertions with &&&& so they can be easily identified.If your solution is completely consistent with the given solution, you need do nothing further with this problem. &#
You should submit a revision on this. Be sure to check my notes and try to respond to them before you look at the discussion at the end.*@