Power of a transverse wave related to rope length

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SUMMARY

The power transmitted down a rope by a transverse wave does not depend on the length of the rope when the linear mass density, tension, and transverse displacement amplitude are constant. For two ropes where one is twice the length of the other, if the shorter rope transmits power P0, the longer rope also transmits power P = P0. This conclusion is drawn from the relationship between power, phase speed, and angular frequency, where the angular frequency remains constant if the same oscillator is used for both ropes.

PREREQUISITES
  • Understanding of transverse wave mechanics
  • Familiarity with the equations of wave power: P = 1/2 uvA²w²
  • Knowledge of linear mass density and its impact on wave speed
  • Basic grasp of angular frequency and its role in wave propagation
NEXT STEPS
  • Study the relationship between wave power and medium properties
  • Explore the effects of tension on wave speed in different materials
  • Learn about the concept of angular frequency in wave mechanics
  • Investigate the implications of varying rope lengths on wave transmission
USEFUL FOR

Students studying physics, particularly those focusing on wave mechanics, as well as educators and anyone interested in understanding the principles of wave power transmission in different mediums.

symphwar
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Homework Statement


Two traveling transverse waves propagate
down two long ropes under the conditions
that the linear mass density, tension, and
transverse displacement amplitude for the two
ropes are the same, but that one rope has
twice the length of the other.
If the shorter rope has a power P0 being
transmitted along its length, then what is the
power, P, being transmitted down the longer
rope?
1. P = 1/4 P0
2. P = 4 P0
3. P = 1/2 P0
4. P = 2 P0
5. P = P0

Homework Equations


P = 1/2 uvA2w2
(u = linear mass density, w = angular frequency, v = phase speed)
v = sqrt(T/u)
(T = tension)

v = w/k
(k = wavenumber = 2pi/wavelength)

The Attempt at a Solution


Given that phase speed is related to tension and linear mass density, I think the values of u, A, and v are the same for both ropes. The only variable remaining is w, and I can't seem to infer what its value might be with the stated information.
Trying to find a relation with w and the given information, I realize I also do not know k or wavelength.
My understanding of a wave's power is that, with a given medium, w is controlled by the person/oscillator generating the wave. Could it be that it is implied w is the same for both waves, so that P = P0?
 
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I think you have the correct answer. The wave traveling down the rope could have any arbitrary value for w, (which would depend on how quickly the person/oscillator moved the rope up and down). So maybe you were supposed to assume the same oscillator was used for both ropes, so w is the same for both, so the power is the same.

In any case, you are right that the power transmitted doesn't depend on the length of the rope.
 
Thanks so much! I was worried about missing something there.
 

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