#$&*
Phy 231
Your 'cq_1_14.1' report has been received. Scroll down through the document to see any comments I might have inserted, and my final comment at the end.
** **
A rubber band begins exerting a tension force when its length is 8 cm. As it is stretched to a length of 10 cm its tension increases with length, more or less steadily, until at the 10 cm length the tension is 3 Newtons.
• Between the 8 cm and 10 cm length, what are the minimum and maximum tensions, and what do you think is the average tension?
answer/question/discussion: ->->->->->->->->->->->-> :
slightly above 0N is the min, 3N is the max. Ave tension is 1.5N
#$&*
• How much work is required to stretch the rubber band from 8 cm to 10 cm?
answer/question/discussion: ->->->->->->->->->->->-> :
3N * 2cm= 6KE
#$&*
@& You wouldn't use the minimum tension on the interval (which is 0) to calculate the work.
It is no more correct to use the maximum tension.*@
@& So what would be an appropriate tension with which to approximate the work done?*@
• During the stretching process is the tension force in the direction of motion or opposite to the direction of motion?
answer/question/discussion: ->->->->->->->->->->->-> :
Opposite the direction of motion
#$&*
• Does the tension force therefore do positive or negative work?
answer/question/discussion: ->->->->->->->->->->->-> :
it does negative work
#$&*
The rubber band is released and as it contracts back to its 8 cm length it exerts its tension force on a domino of mass .02 kg, which is initially at rest.
• Again assuming that the tension force is conservative, how much work does the tension force do on the domino?
answer/question/discussion: ->->->->->->->->->->->-> :
6Joules ?
#$&*
@& If your previous 6 Joules was correct, this would be correct.
However see my note on your previous calculation.
Note also, as I should have pointed out in that response, that a Joule is a Newtom * meter. I don't think your previous calculation involved both Newtons and meters (i.e., be careful about the units).*@
• 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: ->->->->->->->->->->->-> :
0Joules ???
#$&*
@& If the object was released at the 10 cm position and the rubber band did 6 Joules of work on it, then it would be moving.
Think in terms of the work-energy theorem.*@
• At this point how fast will the domino be moving?
answer/question/discussion: ->->->->->->->->->->->-> :
sqrt((6Joules*2)/.02kg)= 24.5m/s???
#$&*
@& Right.
But 6 isn't right, and neither is Joules, per previous notes.*@
*#&!*#&!
@& You're on the right track, but you need to correct a couple of fundamental (and fortunately, easily-corrected) errors.
&#Please see my notes and, unless my notes indicate that revision is optional, submit a copy of this document with revisions and/or questions, and mark your insertions with &&&& (please mark each insertion at the beginning and at the end).
Be sure to include the entire document, including my notes.
If my notes indicate that revision is optional, use your own judgement as to whether a revision will benefit you. &#
*@