# What is the wavelength?

1. Apr 11, 2012

### ixerr

1. The problem statement, all variables and given/known data
Two sinusoidal waves with equal wavelengths travel along a string in opposite directions at 7.72 m/s. The time between two successive instants when the antinodes are at a maximum height is 0.324 s. What is the wavelength (in m)?

2. Relevant equations
vt=x
Also,
Propagation speed = wavelength * frequency = wavelength / period time

3. The attempt at a solution
I tried many, many different ways to solve this equation but ultimately I keep getting the wrong answer.. Here is one of the attempts:
The distance between two successive antinodes or two successive nodes is equal to the wavelength of the wave. I figured out the distance based on the speed of the wave and the time between two antinodes with vt = x (since there is no acceleration).
(7.72)(0.324)= 2.50128 m
Yet it is not the right answer? Can anyone give me any more insight on what I can do..?

2. Apr 11, 2012

### BruceW

The question is a bit vague... does it mean both waves are moving at 7.72 m/s in opposite directions? so their relative velocity is 15.44 m/s ? And it seems to suggest standing waves, but it doesn't mention the end points of the string, so really the two waves could have any phase difference.

If I was guessing, I'd say each of the waves is moving at 7.72 m/s so their relative velocity is 15.44 m/s and I'd guess the situation is standing waves caused by the string being fixed at one end. But what do you think? was there more information?

3. Apr 11, 2012

### ixerr

Yes! :) I got the answer, the velocity was 15.44 m/s. Thanks!

4. Apr 11, 2012

### BruceW

alright, cool