Phy 231
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: Minimum tension = 0 N, and maximum tension = 3 N.
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: Since the rubber band would return to equilibrium at 8 cm if no force opposed it, we find that the 'ds = 10 cm – 8 cm = 2 cm; therefore, with the force of 3 N we have 'dWnet = 3 N * .02 m = .06 J
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: We would set up the equation for KE of an object, and since we know the mass in addition to the energy we have 0.06 J = ½ ( .02 kg) (v)^2; 0.012 J = 0. 2 kg * (v)^2; 6 N = v^2, which gives us 2.45 m/s = v
If instead the rubber band is used to 'shoot' the domino straight upward, then how high will it rise?
answer/question/discussion: When using the equation vf^2 = v0 + 2 a 'ds, we find that 0 = (2.45 m/s)^2 + 2 (-9.8 m/s) 'ds; 0 = 6 m^2/s^2 + -19.6 m/s^2 * 'ds; therefore, - 6 m^2/s^2 = -19.6 m^2/s^2 * 'ds; therefore, 0.306 m = 'ds
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20 minutes
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Good, but note your miscalculation of the work done during the stretch (similar to that on preceding cq qurestion).