Frequency and wavelength of vertical string wave

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Homework Help Overview

The problem involves a long, heavy rope hanging vertically and the behavior of waves traveling up the rope when it is wagged back and forth. Participants are exploring how the frequency and wavelength of the wave change as it moves upward, considering the effects of gravity and tension in the rope.

Discussion Character

  • Exploratory, Assumption checking

Approaches and Questions Raised

  • Participants discuss the relationship between wave velocity, frequency, and wavelength, questioning how gravity affects these properties as the wave travels upward. There is uncertainty about whether frequency or wavelength increases or decreases.

Discussion Status

Participants are actively engaging with the problem, with some suggesting that the velocity of the wave may remain constant while others question this assumption. The discussion is exploring different interpretations of how tension in the rope affects wave properties.

Contextual Notes

There is an underlying assumption regarding the effects of gravity on wave velocity, and participants are considering the properties of the rope that influence wave behavior. The original poster's uncertainty about the relationship between frequency and wavelength is evident.

ming

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


v=fλ

The Attempt at a Solution


Due to gravity the velocity of the wave should be constantly decreasing as it travels upwards. However, I am not sure whether f decreases, λ decreases or something I have never thought of.
 
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Welcome to PF!
ming said:
Due to gravity the velocity of the wave should be constantly decreasing as it travels upwards.
A ball projected vertically upward will slow down due to gravity. But a wave traveling up the rope might not act like the ball. So, you need to reconsider this.

What properties of the rope determine the speed of a wave on the rope?
 
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TSny said:
Welcome to PF!
A ball projected vertically upward will slow down due to gravity. But a wave traveling up the rope might not act like the ball. So, you need to reconsider this.

What properties of the rope determine the speed of a wave on the rope?
So the velocity of the wave stays constant. It also seems the tension of the particles on the string increases as you go up as well. I'm guessing wavelength would increase because of this?
 
ming said:
So the velocity of the wave stays constant.
Why do you say the velocity will remain constant? Did you try to answer the question I posed in post #2?

It also seems the tension of the particles on the string increases as you go up as well.
Yes, the tension increases as you move up the string.
 

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