Halliday, Resnick & Walker — Waves–I: Problem Problem_72

Two sinusoidal 120 Hz waves, of the same frequency and amplitude, are to be sent in the positive direction of an \(x\) axis that is directed along a cord under tension. The waves can be sent in phase, or they can be phase-shifted. Figure 16.24 shows the amplitude \(y'_m\) of the resulting wave versus the distance of the shift (how far one wave is shifted from the other wave). The scale of the vertical axis is set by \(y'_s = 6.0\text{ mm}\). If the equations for the two waves are of the form \(y(x, t) = y_m \sin(kx \pm \omega t)\), what are (a) \(y_m\), (b) \(k\), (c) \(\omega\), and (d) the correct choice of sign in front of \(\omega\)?