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Two waves are propagating on the same very long string. A generator on the right

ID: 2015536 • Letter: T

Question

Two waves are propagating on the same very long string. A generator on the right end creates a wave given by
y=(3.48 cm)cos[(/2)((2.16 m-1)x+(10.24 s-1)t)],

while one at the left end creates the wave given by

y=(3.48 cm)cos[(/2)((2.16 m-1)x-(10.24 s-1)t)].

a) Find the coordinate x>0 of the point closest to the origin on the positive x-axis such that there is no motion (a node). b) Find the coordinate x>0 of the point closest to the origin on the positive x-axis such that the motion of the string reaches a maximum (an antinode). Also, c) What is the total y-displacement at x=0.058 m and t=324 s?

Explanation / Answer

nodes   where cosine funtion is zero or equal to n + /2    then /2 ( 2.16 m-1 x ) = n + /2              ( 1.068 ) x = ( n+ 1/2)               x = ( n+ 1/2)/ ( 1.068 ) when n = 0              = 0.468 , , 1.404, 2.34 ......    anti nodes occure inbeteen these                             ( 1.068) x = n                                           x = n/ 1.068                                   0 , 0.936, 1.87 ........       c) adding two waves             y1 + y2                y=(3.48 cm)cos[(/2)((2.16 m-1)x+(10.24 s-1)t)],+(3.48 cm)cos[(/2)((2.16 m-1)x-(10.24 s-1)t)]. y = 6.96 cos /2 (4.32 m-1 x + 20.48 s-1 t /2) y = 6.96 cm cos /2 ( 2.16 m-1 x + 10.24 s-1 t) put x=0.058 m and t=324 s     y = - 6.83 cm                y=(3.48 cm)cos[(/2)((2.16 m-1)x+(10.24 s-1)t)],+(3.48 cm)cos[(/2)((2.16 m-1)x-(10.24 s-1)t)]. y = 6.96 cos /2 (4.32 m-1 x + 20.48 s-1 t /2) y = 6.96 cm cos /2 ( 2.16 m-1 x + 10.24 s-1 t) put x=0.058 m and t=324 s     y = - 6.83 cm y = 6.96 cos /2 (4.32 m-1 x + 20.48 s-1 t /2) y = 6.96 cm cos /2 ( 2.16 m-1 x + 10.24 s-1 t) put x=0.058 m and t=324 s     y = - 6.83 cm