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PHY 121
Your 'cq_1_20.1' 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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The situation here is similar to that depicted above, though the distances of the rubber bands from the center are different. The die on which the strap rotates is not visible, but is attached to the tabletop; the blue push pin constrains the system to rotate about a vertical axis through the center of the die.
The problem:
The metal strap used in the Angular Velocity of a Strap experiment is constrained by a vertical push pin to rotate about a hole in a die. The die is glued in place to a massive tabletop. A rubber band is attached to a point 15 cm from the axis and stretched so that it exerts a force of 3 Newtons, directed perpendicular to the rod. If this force is unopposed it will accelerate the system rapidly. You want to attach a second rubber band 5 cm from the axis to prevent the system from rotating.
How much force will that rubber band have to exert?
answer/question/discussion: ->->->->->->->->->->->-> n:
I’m not sure how to do this problem.
I know that the forces would have to be equal and opposite, but the distances from the axis leads me to think that it would not simply be 3N.
My only guess is that since the distance is 3 times as far, the force would have to be 3 times as great and in the opposite direction (-9N), but I’m not sure if that makes sense.
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Your conjecture is correct. Very good.
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Once both of these forces are in place and the system is stationary, what (if anything) will happen if the glue holding the die to the tabletop comes loose?
answer/question/discussion: ->->->->->->->->->->->-> n:
I don’t really know. I would imagine some energy would be transferred from the rubber bands if the die is not stationary, but I’m not sure what exactly would happen.
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Solution
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