Wave Motion 5 Question 7

7. The displacement y of a particle executing periodic motion is given by

y=4cos2(12t)sin(1000t)

This expression may be considered to be a result of the superposition of ………. independent harmonic motions.

(1992,2M)

(a) two

(b) three

(c) four

(d) five

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Answer:

Correct Answer: 7. (b)

Solution:

  1. The given equation can be written as

y=2(2cos2t2)sin(1000t)y=2(cost+1)sin(1000t)=2costsin1000t+2sin(1000t)=sin(1001t)+sin(999t)+2sin(1000t)

i.e. the given expression is a result of superposition of three independent harmonic motions of angular frequencies 999, 1000 and 1001rad/s.



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