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?
8*3=24
10*3=30
###This should be 0 for minimum tension and 3 Newtons for maximum tension
answer/question/discussion:
• Assuming that the tension in the rubber band is 100% conservative (which is not actually the case) what is its elastic potential energy at the 10 cm length?
100/10=10
###’dW=F_ave*’ds ‘dW= 1.5N*2cm=3N*cm
answer/question/discussion:
• If all this potential energy is transferred to the kinetic energy of an initially stationary 20 gram domino, what will be the velocity of the domino?
20/10=2
###This is 1/2mv^2=KE which would be v=sqrt(2*KE/m)=sqrt(2*.03Joules/.02Kg)=1.7m/s^2
answer/question/discussion:
• If instead the rubber band is used to 'shoot' the domino straight upward, then how high will it rise?
###This would be ‘dy=.03Joules/mg=.03Joules/.02kg*9.8m/s^2=.15m
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Good revision.