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The frequency of the first harmonic on a standing wave is f. The length and tension are doubled, what affect does this have on the frequency?

I’ve spend the best part of an hour on this and it’s a one marker. Please help, with an explication.
Original post by -Mathematician-
The frequency of the first harmonic on a standing wave is f. The length and tension are doubled, what affect does this have on the frequency?

I’ve spend the best part of an hour on this and it’s a one marker. Please help, with an explication.



I am assuming that you are talking about the string that is fixed at both ends. The first harmonic is given by

f1=12LTμ f_1=\dfrac{1}{2L} \sqrt{\dfrac{T}{\mu }}

where L is the length of the string, T is the tension and μ is the “mass density” or mass per unit length.

I believe that you can work from here to find the answer that is required by the question.
I got roo2/2 but this is wrong? The length gives 1/2 then the tension fives root2 surely?
Original post by -Mathematician-
I got roo2/2 but this is wrong? The length gives 1/2 then the tension fives root2 surely?


What is wrong? Is this a MCQ or a qualitative question?

Not sure what you are writing about.

It would be better that you post the full question.
(edited 6 years ago)
62D49C48-0705-499D-BB53-8EC084C707A7.jpg.jpeg
Original post by -Mathematician-
62D49C48-0705-499D-BB53-8EC084C707A7.jpg.jpeg



Please brush up your maths skill and learn how to simplify the radical.

Spoiler

Reply 6
Original post by Eimmanuel
Please brush up your maths skill and learn how to simplify the radical.

Spoiler




how come if you let mew=m/l doesn't that change the answer I know mew is constant but is it not allowed to make this substitution?
Original post by IsaiahD
how come if you let mew=m/l doesn't that change the answer I know mew is constant but is it not allowed to make this substitution?



Yes, by letting μ = M/L. It will change the answer from A to B. If you want to consider the mass does not change when the length of the string is doubled, I am good with it.

As far as I know, if we double the length without keeping the μ constant but the mass is constant, we can break the string “easily”.

I can be wrong about the answer. :smile:
Reply 8
Original post by Eimmanuel
Yes, by letting μ = M/L. It will change the answer from A to B. If you want to consider the mass does not change when the length of the string is doubled, I am good with it.

As far as I know, if we double the length without keeping the μ constant but the mass is constant, we can break the string “easily”.

I can be wrong about the answer. :smile:


im not sure tbh, its just when you use density in equations you are allowed to have It as mass/volume and continue with calculations like that so im unsure here im pretty sure you write M/L

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