# Homework Help: Actual displacement of a wave particle

1. Dec 12, 2013

### Jon.G

1. The problem statement, all variables and given/known data
The end of a stretched string is forced to vibrate with a transverse displacement with A= 0.30 m and ω = 9.0 rad s-1. If the tension of the string is T = 4.0 N, and the mass per unit length is µ= 1.250 g m-1, calculate

(a) the wave velocity,

(b) the frequency of oscillation,

(c) the wavelength, and

(d) the displacement of the string at x = 2.0 m from the source at the time t = 100 ms after the oscillation commences.
Assume that the wave is travelling from left to right.

The attempt at a solution
a.) v=√(T/μ) giving me a wavespeed of 56.6 ms-1
b.)ω=2∏f giving me a frequency of 1.43 Hz
c.)v=fλ giving me a wavelength of 39.6 m
d.)This is where I'm stuck :( I would think of using the equation vertical displacement,
y=Asin(kx-ωt) except I don't know how to find k
Any help appreciated.

2. Dec 12, 2013

### Simon Bridge

If you put t=0, then you have y=Asin(kx)
... then when x=0, y=0 right?
... when x=λ, what is y equal to (hint: definition of wavelength)?
... therefore what is kλ equal to?