Solving Wave-Related Trouble in Physics

  • Thread starter Thread starter Great_White
  • Start date Start date
AI Thread Summary
The discussion revolves around identifying the correct representation of standing waves on a guitar string in its fundamental frequency. The student grapples with understanding wavelength, initially believing it to be the distance between two antinodes, but later learns it is measured from node to node. Confusion arises over which graphs accurately depict the fundamental mode of vibration, with options suggesting various combinations of the figures. The conclusion leans towards options that include graphs showing the first and second modes, as they better illustrate the natural frequencies of the string. Clarification on the definitions and visual representations of standing waves is sought to resolve the uncertainties.
Great_White
Messages
4
Reaction score
0
Hello,

I've been working out this question but I'm not sure about the answer. It relates to waves, which is something I've yet to deal with in school. It says:

When you disturb a guitar string you'll create a standing wave in its fundamental sound. Three students draw the shape of the string and different instances, as shown by the graph(...see attachment?), admitting that the string vibrates in its fundamental sound (...fundamental frequency?).

Out of these figures, the correct one is...

a. 3, because nodes are formed at the ends of the string
b. 1 and 2, because the represent the initial wave and its reflection
c. 2 and 3, because the fulfill the conditions of the fundamental mode
d. only 1, because it's the only one that shows a complete wavelength

(I just translated this --no quick-translator, mind you-- so pardon me if some terms are a bit off --I did research some, like standing wave and wavelength, though...)

Now, after doing some research on the net and reading my Wilson's physics for a bit, I had come to the conclusion that you can't appreciate a complete wavelength on the firs graph... I though wavelength was the distance between two antinodes, but alas, it seems it isn't... I've found somewhere else that wavelength is actually node-to-node. What's the correct form? :confused:

a. doesn't mean anything . That leaves b and c (and... d?). Since a guitar string can have various harmonics, both would be partially correct... however, I've come to the conclusion that the first graph is incorrect! It's not a complete harmonic (it should look like two horizontal ovals, right?). That'd leave c, right? I'm not too sure, and that's why I'm asking :smile:

So, I'd appreciate if you folks could help me. Thanks in advance.
 
Physics news on Phys.org
Great_White said:
I though wavelength was the distance between two antinodes, but alas, it seems it isn't... I've found somewhere else that wavelength is actually node-to-node. What's the correct form?

I don't think this really matters. According to http://www.wave-guide.org/archives/waveguide_3/glossary.html, a wavelength is the distance between two consecutive points on a sinusoidal wave that are in phase; measured in meters.e

edit: BTW, your attachment is nowhere to be seen.
 
Last edited:
OH c'mon! Gimme a couple of minutes to find the image...
 
http://img.photobucket.com/albums/v228/beto2/wave.bmp
that should help...
 
Last edited by a moderator:
BTW, recon, the "OH c'mon" thing wasn't directed at you, it was annoyance toward the non-working attachment...

(thought I'd clarify...)
 
The top picture, to me, looks like 2f of the middle picture. I would venture to say that it is 1 and 2 because the two show the first and second modes of the natural frequency.
 
Thread 'Variable mass system : water sprayed into a moving container'
Starting with the mass considerations #m(t)# is mass of water #M_{c}# mass of container and #M(t)# mass of total system $$M(t) = M_{C} + m(t)$$ $$\Rightarrow \frac{dM(t)}{dt} = \frac{dm(t)}{dt}$$ $$P_i = Mv + u \, dm$$ $$P_f = (M + dm)(v + dv)$$ $$\Delta P = M \, dv + (v - u) \, dm$$ $$F = \frac{dP}{dt} = M \frac{dv}{dt} + (v - u) \frac{dm}{dt}$$ $$F = u \frac{dm}{dt} = \rho A u^2$$ from conservation of momentum , the cannon recoils with the same force which it applies. $$\quad \frac{dm}{dt}...
Back
Top