What Is the Phase Angle of a Wave Traveling on a String?

[physicsgrouch]

A transverse, sinusoidal wave is traveling along a string. It moves in the negative x-direction, and it has an amplitude of 5 cm. At time t=0, the point at x=0 is at a displacement of 4 cm and is traveling upward. What is the phase angle in degrees?

Homework Equations

x = A*cos(\omega*t+\phi)

The Attempt at a Solution

At t=0, \omega*t = 0, so x = A*cos(\phi). Therefore, \phi = arccos(x/A) = arccos(.8) = 36.87.

The acceleration is negative and the velocity is positive, so the angle is 360 - 36.87 = 323.13 degrees, right?

 

[physixguru]

The equation you just used is not trustworthy for waves.It can be only generalized to SHM.

You must use wave equations to be more sure in your answers.

y= A sin ( k*x-omega*t + phase angle)