Frequency and wavelength of a wave on a vertical rope

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SUMMARY

The discussion focuses on the behavior of waves on a vertical rope, specifically how frequency and wavelength change as the wave travels upward. As tension increases with height, the phase velocity (C) also increases, leading to the conclusion that while the frequency remains constant at the lower end, the wavelength must increase to satisfy the equation C = fλ. If the frequency were to increase, it would result in a decrease in the period, which contradicts the initial condition of constant frequency.

PREREQUISITES
  • Understanding of wave mechanics, specifically wave properties such as frequency and wavelength.
  • Familiarity with the equation C=√(T/p) for wave speed in a medium.
  • Knowledge of the relationship between frequency (f), wavelength (λ), and wave speed (C) through the equation C = fλ.
  • Basic grasp of tension in a rope and its effect on wave propagation.
NEXT STEPS
  • Research the implications of varying tension on wave speed in different mediums.
  • Explore the concept of wave reflection and transmission at boundaries in ropes.
  • Study the effects of frequency modulation on wave characteristics in various physical systems.
  • Investigate the mathematical derivation of wave equations in non-uniform media.
USEFUL FOR

Students studying physics, particularly those focusing on wave mechanics, as well as educators looking for practical examples of wave behavior in real-world applications.

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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