Frequency and wavelength of a wave on a vertical rope

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Homework Help Overview

The problem involves a long, heavy rope hanging vertically, where a wave is generated by wagging the lower end with a constant frequency. The discussion centers on how the frequency and wavelength of the wave change as it travels up the rope, particularly in relation to the tension in the rope and the implications of a constant frequency.

Discussion Character

  • Exploratory, Assumption checking, Conceptual clarification

Approaches and Questions Raised

  • Participants discuss the relationship between tension, frequency, and wavelength, questioning whether the frequency remains constant as the wave travels up the rope. Some suggest that if the frequency were not constant, it could lead to absurd consequences.

Discussion Status

The discussion is ongoing, with participants exploring different interpretations of the problem. Some have raised questions about the implications of changing frequency and are considering the effects of wave pulses traveling up the rope.

Contextual Notes

There is a focus on the tension in the rope increasing with height, and participants are examining the relationship between frequency and wavelength without reaching a definitive conclusion. The original poster's mention of homework constraints suggests that certain assumptions must be adhered to in their analysis.

Helloworld
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Homework Statement


A long, heavy rope hangs straight down from a high balcony on an apartment building. The lower end of the rope hangs about 1.0 m above the ground. If you grab onto the lower end and waggle it back and forth with constant frequency f, a wave travels up the rope. What would happen to the frequency and wavelength of the wave as it travels up the rope? For each property, state whether it would increase, decrease or remain the same, and explain briefly.

Homework Equations


C=√(T/p), C = fλ
f=ω/2π, λ=2π/k

The Attempt at a Solution


The tension increases as we go up the rope since the force at the top is exerted to counteract the weight force of the remaining rope. So the phase velocity C increases meaning that either the frequency or the wavelength must increase to balance the equation C = fλ. The question is, which one will increase? It is stated in the question that the frequency is constant but will it be constant as it travels up the rope?
 
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Can you perhaps think of any obviously absurd consequences that would result if the frequency was not constant?
 
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Orodruin said:
Can you perhaps think of any obviously absurd consequences that would result if the frequency was not constant?

Then maybe the frequency will increase because the period decrease(amplitude of the wave decrease as well)?
 
I feel as if you are just guessing rather than thinking it through.

Consider a series of pulses from the bottom to the top sent with a separation of 1 s. How far apart would those pulses be at the top of the rope if frequency increased by a factor of 2?
 
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Orodruin said:
I feel as if you are just guessing rather than thinking it through.

Sorry about this. To be honest, I have no clue after the C. I will do more research to answer the question about the pulses
Orodruin said:
Consider a series of pulses from the bottom to the top sent with a separation of 1 s. How far apart would those pulses be at the top of the rope if frequency increased by a factor of 2?
So T = 1/f and if frequency doubled, T would be 0.5s thus 0.5 seconds apart
 
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