# Traveling wave problem

1. Feb 21, 2015

### hobmarcus

1. The problem statement, all variables and given/known data

Two points on a string are observed as a traveling wave passes. The points are at x1 = 0 and x2 = 1 m. The two points are known to be less than one wavelength apart. The transverse motions of the two points are observed to be

y1=0.2 sin 3πt

y2=0.2 sin (3πt+π/8)

(a) What is the frequency of this wave in hertz?

(b) What is the wavelength?

(c) What is the wave speed?

(d) Can you tell if this wave is moving to the right or to the left? If so, which way is it moving?

The attempt at a solution

For part (a), I simply found the frequency by knowing that ω=3π and ω =2πf.
However, for part (b), I could not find the text's book answer by just using k=2π/λ
the answer's from text book for b is .

Any good explanations or hints for me? I have been reading the textbook again and again, but still can't find why.
(textbook = AP FENCH, vibrations and wave)

2. Feb 21, 2015

### vela

Staff Emeritus
How exactly did you use $k = \frac{2\pi}\lambda$?

3. Feb 21, 2015

### hobmarcus

I assumed that π/8 = k and just find λ with k=2π/λ?

4. Feb 21, 2015

### vela

Staff Emeritus
Remember sin is periodic, so that's not the only possible solution.

5. Feb 21, 2015

### hobmarcus

So.. what you mean is , I should assume that k=π/8 +2nπ ?

Also, how about part D? is there anyway to tell where is the wave going?