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Phy 241
Your 'cq_1_15.1' 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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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?
answer/question/discussion: ->->->->->->->->->->->-> :
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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?
answer/question/discussion: ->->->->->->->->->->->-> :
PE = F_ave*'ds
= 1.5 N * 0.02 m
= .03 Joules
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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?
answer/question/discussion: ->->->->->->->->->->->-> :
0.03 N-m = 1/2*m*v^2
v = sqrt[(0.03kg-m^2/s^2)/(0.01kg)]
= sqrt(3) = 1.73 m/s
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If instead the rubber band is used to 'shoot' the domino straight upward, then how high will it rise?
answer/question/discussion: ->->->->->->->->->->->-> :
v_0 = 1.73 m/s
v_f = 0 m/s
w = m*g
= 9.81m/s^2*0.02kg = .1962 N
a = g
W = F*'ds
= m*a*'ds
'ds = F/mg
= 0.3 N-m / 0.1962 N
= 0.153 m = 15.3 cm
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For University Physics students:
Why does it make sense to say that the PE change is equal to the integral of the force vs. position function over an appropriate interval, and what is the
appropriate interval?
answer/question/discussion: ->->->->->->->->->->->-> :
Just like a velocity vs time graph yeilds acceleration and the area below the curve yields displacement, So a graph for force vs position yields Work. PE can also
be thought of as displacement, so the area under the curve is displacement or PE or simply work, which basically is the same as long as it is thought in terms of a change in potential energy.
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&#Very good responses. Let me know if you have questions. &#