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Two traveling waves are generated on the same taut string. Individually, the two

ID: 2108572 • Letter: T

Question

Two traveling waves are generated on the same taut string. Individually, the two traveling waves can be described by the following two equations:


Y2(x,t) = (4.03 cm) sin (k2x - (4.92 rad/s) t + Θ2)

Y1(x,t) = (1.25 cm) sin (k1x + (0.278 rad/s) t + Θ1)

If both of the above traveling waves exist on the string at the same time, what is the maximum positive displacement that a point on the string can ever have? (answer: 5.28 cm)

What is the smallest positive values of the unknown phase constants (in radians) such that the above displacement occurs at the orgin (x=0) at the t = 3.33 s?

Θ2 = _______ rad


I have found the correct answers for the maxium positive displacement that a point on the string can have (5.28 cm) and theta 1 but I need help finding theta 2. Thanks.

Explanation / Answer

This solution is based on the observation that two sinewaves of equal amplitude but differing phase have a maximum absolute sum where they intersect; this is shown by the fact that their slopes are equal in terms of |dy/dx| at the intersection, and as you move away, the decreasing function has a steeper slope than the increasing one. Any time that happens, you have a maximum sum.So we can say in this case that each amplitude = 0.725A. Then half the phase difference ??/2 = arccos(0.725) = 0.75976