course PHY 121
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?
8* 3 =24
10*3=30
###This should be 0N+3N/2=1.5N
answer/question/discussion:
• How much work is required to stretch the rubber band from 8 cm to 10 cm?
9*3=27
###10cm-8cm=2cm
1.5N*2cm=3.0N*cm=.03Joules
answer/question/discussion:
• During the stretching process is the tension force in the direction of motion or opposite to the direction of motion?
Opposite of the direction of motion
###this should be in the same direction of motion
answer/question/discussion:
• Does the tension force therefore do positive or negative work?
Negative
###This would be positive
answer/question/discussion:
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?
8*.02=.16
###This would be +.03Joules
answer/question/discussion:
• 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?
8*1.6=12.8
###This should be the increase of .03J
answer/question/discussion:
• At this point how fast will the domino be moving?
###This is would be v=sqrt(2*.03J/.02kg)=sqrt (3m^2/s^2)=1.7m/s
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