course Phy 231
June 294:07 pm
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:
F = kx
3 = k*.1
k = 30
F = kx
F = 30*.08
F = 2.4
The max tension is given at 3N, the minimum tension is 2.4N.
• 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:
If the system is conservative, the potential energy would be equal to the total work done. Calculating the total work, we get W = F*d = 3*10 = 30J. That means the elastic potential energy would be 30J at 10cm.
• 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:
K = 1/2 mv^2
30J = 1/2 * .02 v^2
30 = .01v^2
3000 = v^2
v = 54.77 m/s
• If instead the rubber band is used to 'shoot' the domino straight upward, then how high will it rise?
answer/question/discussion:
F = ma
3 = .02*a
a = 150
U = mgh
30J = .02*150*h
30 = 3h
h = 10 m
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See also my notes on the preceding 'seed' question. You've repeated the error of the preceding regarding the equilibrium position; and you have some errors in units. But most of your thinking is correct.
Check out the link below:
&#Please compare your solutions with the expanded discussion at the link
Solution
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