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# waves watch

1. given equation of a transverse wave is:
y=8*cos{240(pi*t - x/312)}
The question is what is the wavelength, frequency and velocity of wave?

i can solve equations if it's in terms of sine as equation of wave is given by:
y=asin(wt-kx)..
2. (Original post by aachal)
given equation of a transverse wave is:
y=8*cos{240(pi*t - x/312)}
The question is what is the wavelength, frequency and velocity of wave?

i can solve equations if it's in terms of sine as equation of wave is given by:
y=asin(wt-kx)..
I have no idea on a lot of the stuff above. But why not use v=f X lambda to work out wavelength. You already have frequency and velocity. This could help.
3. this is how i tried solving:
w=240*pi
2*pi*f=240*pi
thus,f=120 Hz
and
240/312=2*pi/lamda
thus
, lamda=2.6m
As, v=lamda*f
v=2.6*120=312m/s
well, i got the velocity correct but the value of frequency was wrong. the same thing happened in similar other questions
i hope someone can help.......
4. (Original post by aachal)
this is how i tried solving:
w=240*pi
2*pi*f=240*pi
thus,f=120 Hz
and
240/312=2*pi/lamda
thus
, lamda=2.6m
As, v=lamda*f
v=2.6*120=312m/s
well, i got the velocity correct but the value of frequency was wrong. the same thing happened in similar other questions
i hope someone can help.......
Cos(x) = Sin(Pi/2-x)
5. (Original post by joostan)
Cos(x) = Sin(Pi/2-x)
yes, but can you use it to find the answer?
6. Sorry if this is slightly unrelated, but is this A Level or degree or...?
7. I think you have the equation wrong, the answers you've given are consistent with:

remember that the phase velocity of a wave is:

and k is the wavenumber defined as

(Original post by aachal)
i can solve equations if it's in terms of sine as equation of wave is given by:
y=asin(wt-kx)..
Remember that sine and cosine are just shifts of one another so a wave of the form has the same properties as the sine wave of the same form except all the points are shifted.
8. (Original post by An Ignorant Duck)
Sorry if this is slightly unrelated, but is this A Level or degree or...?
no, it is'nt A Level exactly but equivalent to it. what i mean is it's from course of grade 12, higher secondary level .....sorry if i got u confused..
9. (Original post by alice_in_video)
I think you have the equation wrong, the answers you've given are consistent with:

remember that the phase velocity of a wave is:

and k is the wavenumber defined as

Remember that sine and cosine are just shifts of one another so a wave of the form has the same properties as the sine wave of the same form except all the points are shifted.
yes, you're right about the fact that wave in terms of sine and cosine have same properties. the equation might be wrong too. but here are some other questions in which i get the same problems.
for example: a stationary wave is given by the equation:

y=6 sin (2*pi*x/6) cos(60*pi*t)
now when i compare it with standard equation i get the wavelength right but the frequency is again in correct as compared to the answer given in the book.ans is: frequency of original progressive wave is 80Hz and wavelength is 3cm.

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