# Homework Help: Mechanical Waves- PHASE(EASY)

1. Aug 25, 2009

### kpx001

1. The problem statement, all variables and given/known data
The figure shows a snapshot of three waves traveling along a string, where x,t are in SI units. The phases for the waves are given by... the picture and problem is in this link
http://img339.imageshack.us/img339/2407/phys1prob.th.png [Broken]

2. Relevant equations
(kx-wt)
lambda=2pi/k

3. The attempt at a solution

Basiclly I think I can solve the rest if i understand this problem. The wavelength= 2pi ?
but when i solve for k... k=2pi/lambda, k is one. the answer should give me that k is 2, and the only way i can get that is if the wavelength is pi. Can anyone please help me to understand this?

Last edited by a moderator: May 4, 2017
2. Aug 25, 2009

### kuruman

If k = 2π / λ then the wave with the smallest k corresponds to the longest wavelength.

So ...

3. Aug 25, 2009

### kpx001

I now understand the relationship, but I want to know how to do it the mathematical way.

4. Aug 25, 2009

### kuruman

How do you mean "mathematical way"? The information that you are given is in a picture that you have to interpret.

5. Aug 26, 2009

### kpx001

oh so it would be k=2n/lambda ... the 2n = 2(2pi) and the lambda = 2pi?

6. Aug 26, 2009

### kuruman

I don't know what you mean by this. The wavelength is inversely proportional to k. Therefore long wavelength means small k. Look at the picture. Which of the three waves has the longest wavelength? Then look at the phases. Which one has the smallest k, (a), (b) or (c)? Match the two. Continue with the other two waves.