- #1
roam
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Homework Statement
Two displacement waves with the same period T = 3.0 s are described mathematically by:
y1 = (10.0 m) cos[2πt/T + π]
y2 = (9.0 m) cos[2πt/T + 2π]
What is the resultant displacement at time t = 6.0 s?
The Attempt at a Solution
I tried adding up
y1 + y2 = 19 cos [2πt/T + 3π]
But the answer I get is wrong. I also tried the following formula from my texybook which is supposed to give the resultant of two traveling sinusoidal waves:
[tex]y=2Acos \left( \frac{\phi}{2} \right) sin \left( kx-\omega t + \frac{\phi}{2} \right)[/tex]
I don't know what the phase constant (φ) is, so I assume it is zero since the waves are in phase, then cos(φ/2)=cos(0)=1.
When I plug in the numbers the formula then becomes
y=6sin(3π+2π6/3)
Again, this produces the wrong answer, the correct answer should be -1.0 m. What's wrong with my calculations?