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YMMMA
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Why are no equations needed? I would need an equation or two to solve this question. Can you say what it/they might be? And then can you apply the equation(s) to check your answer?YMMMA said:Homework Equations
No equation needed.
I will search, then.berkeman said:Why are no equations needed? I would need an equation or two to solve this question. Can you say what it/they might be? And then can you apply the equation(s) to check your answer?
The equation you posted is for a doubly-constrained rope, I believe, fixed at both ends. The problem in your OP is a little different. It seems to be asking about a long combination of two ropes, with the first part lighter (lower density) and the 2nd part heavier (higher linear density). The excitation at the left will generate transverse waves that will travel to the right with some frequency, velocity and wavelength. There will be a partial reflection of that traveling wave at the discontinuity between the two ropes, but you can ignore that for this question, I believe.YMMMA said:Here, the density increases in the thick rope causing the speed decreases. If the speed decreases, will the frequency decrease based on the rule?
Think about the oscillation frequency at the join. How must this compare with the frequencies of adjacent parts?YMMMA said:If it is a thick rope the frequency decreses;
How would you think it possible for one bit of rope to be going up and down at one frequency and the adjacent bit going up and down at a different frequency? If that happenedYMMMA said:If the speed decreases, will the frequency decrease based on the rule?
I have seen all, thanks for your helpberkeman said:The equation you posted is for a doubly-constrained rope, I believe, fixed at both ends. The problem in your OP is a little different. It seems to be asking about a long combination of two ropes, with the first part lighter (lower density) and the 2nd part heavier (higher linear density). The excitation at the left will generate transverse waves that will travel to the right with some frequency, velocity and wavelength. There will be a partial reflection of that traveling wave at the discontinuity between the two ropes, but you can ignore that for this question, I believe.
Now, what is the relationship between frequency, velocity and wavelength for a traveling wave? And if the left end of the light rope is being shaken up and down at some frequency, what would happen if the frequency changed at the place where the two ropes join?
After you think about that for a bit, check out this paper for information on a slightly different equation that you should consider...
http://www.cmp.caltech.edu/refael/league/wave-speed.pdf
And after reading that and thinking more about your answer, you can check out this nice summary post by @sophiecentaur in another thread about wave propagation and transitioning between different regions (in the case of that thread, it's EM waves and changing impedances of media that it is propagating through, but it still is very similar to this question of yours):
https://www.physicsforums.com/threads/refraction-of-a-wave.957400/#post-6071022
Something else that should be born in mind is the fact that, when the wave encounters a change in density (and hence wave impedance) there will be a reflection of some of the incident energy at the transition. A single pulse will show this reflection and a continuous wave will show a change in amplitude at the interface, in order that the net energy flow into the transition equals the flow out of the transition.YMMMA said:Aha, now I can clearly understand that at the join the frequency will continue while the wavelength can change. For the speed, it is proportional to the square root of the tension over the density. Therefore, the speed decreases with increasing density.
Thank you all!
Understood.sophiecentaur said:Something else that should be born in mind is the fact that, when the wave encounters a change in density (and hence wave impedance) there will be a reflection of some of the incident energy at the transition. A single pulse will show this reflection and a continuous wave will show a change in amplitude at the interface, in order that the net energy flow into the transition equals the flow out of the transition.
The speed of a wave in a rope is directly related to the tension and density of the rope. In general, a thicker rope will have a higher density and therefore a higher wave speed compared to a thin rope.
The frequency of a wave in a rope is determined by the source of the wave and the properties of the rope itself, such as tension and density. Therefore, the frequency of a wave in a thick rope may be different from that in a thin rope depending on these factors.
The wavelength of a wave is inversely proportional to the frequency and directly proportional to the wave speed. Therefore, in a thick rope with a higher wave speed, the wavelength may be shorter compared to a thin rope with a lower wave speed.
The energy of a wave is proportional to the square of the wave amplitude. In a thick rope, the amplitude may be larger due to its higher wave speed, resulting in a higher energy compared to a thin rope.
Yes, the speed and frequency of a wave in a rope can be altered by changing the properties of the rope, such as tension and density, or by changing the source of the wave. For example, plucking a thicker rope with more force will result in a higher frequency and speed of the wave.