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PHY 231
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: ->->->->->->->->->->->-> :
This second rubber band will have to exert an equal and opposite force, enough to restrict the angular velocity and subsequent acceleration caused by the first rubber band. Thus, I would say that the second rubber band would only have to exert 1 N of force, because it is only 5 cm away from the axis of rotation, versus the 15 cm of distance of the first rubber band.
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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: ->->->->->->->->->->->-> :
The entire balance of the system will be compromised. The die will cause unsteady motion. The metal strap may no longer rotate evenly, fluctuating in height at its ends and possibly spinning off the die. Consequently, there will be a shift from equilibrium, of the two forces in opposition. The entire system will collapse, if the glue comes loose, and the die begins to move, as it likely will, from its position underneath the metal strap.
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