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 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: ->->->->->->->->->->->-> :
The rubber bands are going to be doing equal and opposite amounts of work so that the net force on the system is 0N and so that the strap won’t move.
The first band is pulling in the anticlockwise (positive) direction. This means that the other band will have to move in the clockwise (negative) direction to keep the system stationary.
15cm * 3N = 5cm * x N
45 N cm = 5x N xm
X = 9 Newtons (It has to be in the opposite direction)
The second band will be exerting -9 N of force
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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: ->->->->->->->->->->->-> :
If the glue on the die fails then both of the rubber bands will spring back to the original length and pull the strap towards them. Since they are both pulling on the same side of the strap, the strap should move in the direction of the bands.
one band exerts more force than the other, so there would also be some rotation
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20 minutes
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&#Very good responses. Let me know if you have questions. &#