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Isaac Physics question - standing waves

I need some help on an Isaac physics question. It’s super simple but I can’t seem to get it correct, so if anyone could point out my mistakes I would be super grateful!
image.jpg
The answer is in 3sf btw
(edited 2 months ago)
Original post by Halleline
I need some help on an Isaac physics question. It’s super simple but I can’t seem to get it correct, so if anyone could point out my mistakes I would be super grateful!
image.jpg
The answer is in 3sf btw


Your second equation does not make sense.
It is your algebraic manipulation that causes the problem.

f3 = 3f1
I use f1 as the fundamental frequency.
f1=12LTμ f_1 = \frac{1}{2L} \sqrt{\frac{T}{\mu}}

When you move 2L from right to left, they should become numerator.

Maybe you want to practise your algebra... :smile:
(edited 2 months ago)
Reply 2
Original post by Eimmanuel
Your second equation does not make sense.
It is your algebraic manipulation that causes the problem.
f3 = 3f1
I use f1 as the fundamental frequency.
f1=12LTμ f_1 = \frac{1}{2L} \sqrt{\frac{T}{\mu}}
When you move 2L from right to left, they should become numerator.
Maybe you want to practise your algebra... :smile:

IMG_8765.jpeg
It does become the numerator as you take the reciprocal of 1/2L so I’m not sure what equation you’re referring to ?
Isaac Physics question - standing waves image_edit.jpg

Original post by Halleline
IMG_8765.jpeg
It does become the numerator as you take the reciprocal of 1/2L so I’m not sure what equation you’re referring to ?
Reply 4
Original post by Eimmanuel
Isaac Physics question - standing waves image_edit.jpg

Yeah that is what I did but when I further rearrange for mu , it says it’s incorrect . But I also used the equation my professor gave me and that’s coming out wrong too ? So I either can’t do significant figures anymore, I can’t convert ( only length from cm -> m though ) or my professor can’t do algebra either.

So I am even more confused then before 😀
(edited 2 months ago)
Original post by Halleline
Yeah that is what I did but when I further rearrange for mu , it says it’s incorrect . But I also used the equation my professor gave me and that’s coming out wrong too ? So I either can’t do significant figures anymore, I can’t convert ( only length from cm -> m though ) or my professor can’t do algebra either.

So I am even more confused then before 😀

When you make μ \mu the subject for
fn=n2LTμ f_n = \frac{n}{2L} \sqrt{\frac{T}{\mu}} ,

what do you get?

The μ \mu equation that your prof gets is incorrect. You can do a "unit analysis" to verify it.

The SI unit for μ \mu is kg/m.

Can you post the link for the question?
Reply 7
Original post by Eimmanuel
When you make μ \mu the subject for
fn=n2LTμ f_n = \frac{n}{2L} \sqrt{\frac{T}{\mu}} ,
what do you get?
The μ \mu equation that your prof gets is incorrect. You can do a "unit analysis" to verify it.
The SI unit for μ \mu is kg/m.
Can you post the link for the question?
that’s the link:
https://isaacphysics.org/questions/phys_linking_15_q3?boardhttps://isaacphysics.org/questions/phys_linking_15_q3?board=bfl22_standing_waves_1=bfl22_standing_waves_1
(edited 2 months ago)
Reply 8
Original post by Eimmanuel
When you make μ \mu the subject for
fn=n2LTμ f_n = \frac{n}{2L} \sqrt{\frac{T}{\mu}} ,
what do you get?
The μ \mu equation that your prof gets is incorrect. You can do a "unit analysis" to verify it.
The SI unit for μ \mu is kg/m.
Can you post the link for the question?
This is what I get rearranging
IMG_8769.jpeg
Reply 9
Original post by Halleline
This is what I get rearranging
IMG_8769.jpeg

IMG_8770.jpeg
Used that equation but it’s incorrect too
Original post by Halleline
This is what I get rearranging
IMG_8769.jpeg


Isaac Physics question - standing waves image_01_edit.jpg
Not sure why you bring L^2 to the numerator.
Or else the second last equation is good.
Original post by Halleline
IMG_8770.jpeg
Used that equation but it’s incorrect too


You need to practise your algebra manipulation skills.

You need to use SI in using the equation or else you will have "units mismatch" (common mistakes in A level), do the conversion from kg/m to g/m as the final step.
Reply 13
Original post by Eimmanuel
Isaac Physics question - standing waves image_01_edit.jpg
Not sure why you bring L^2 to the numerator.
Or else the second last equation is good.

I thought you had to take the reciprocal no ? Oh well
tbh I’m normally pretty good with algebra , must of been a while since I last revised it , I’ll have to do again soon.
Thank you for all your help though , Im very grateful!!

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