Homework Help: Transverse wave question

1. Oct 9, 2011

Qudos

1. The problem statement, all variables and given/known data
A transverse sinusoidal wave is moving along a string in the positive direction of an x axis with a speed of 80 m/s. At t = 0, the string particle at x = 0 has a transverse displacement of 4.2 cm from its equilibrium position and is not moving. The maximum transverse speed of the string particle at x = 0 is 18 m/s.
It asks to solve for f,λ,$y_{m}$,k,ω, and $\phi$ in the wave formula

2. Relevant equations

y(x, t) = $y_{m}$ sin(kx ± ωt + $\phi$)

3. The attempt at a solution
Since it says at t and x = 0 the displacement is 4.2cm and stopped moving i assumed that meant that it had reached its max displacement. I then used $u_m=ωy_m$
for the max transverse speed and solved for ω, which i put into the formula
f=$\frac{ω}{2\pi}$ which gave me $0.00367s^-1$, and solving for wavelength using $λ=\frac{v}{f}$ gave me 21827m which doesn't seem right, i'm pretty sure i'm doing something wrong, any help would be appreciated.

thanks

Oh and btw i converted all the cm to m before calculating.

2. Oct 10, 2011

Spinnor

You wrote,

u_m=ωy_m (why can't I copy and paste your formulas intact? Oh well)

Did you mix units, the displacement was given in cm and the velocity in m/s ??? We want everything in cm or m.

3. Oct 10, 2011

Qudos

Yes i converted 4.2cm to 0.042m, then divided 18m/s by 0.042m to get a very large ω value of 428.6

4. Oct 10, 2011

Qudos

Ok, i calculated again and i think i switched the denominator with the numerator in something. Seems to be more reasonable now.
Thanks