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Waves

Question
CBSEENPH11026119

 A particle is executing two different simple harmonic motions, mutually perpendicular, of different amplitudes and having phase difference of π2 The path of the particle will be

  • circular

  • straight line

  • parabolic

  • elliptical

Solution

D.

elliptical

Let two perpendicular simple harmonic motions arex = A sin ωt        ....(1)y= B sin ωt +ϕ    ...(2)from equation (1) sin ωt   =xAsin 2ωt  + cos2 ωt  = 1cos2 ωt  = 1 - x2A2 cosωt  =1-x2A2   2yB = sin ωt  cosϕ + cosωt  sinϕyB-xAcosϕ =1-x2A2 sinϕsquaring on both sidey2B2 +x2A2cos2ϕ -2 yB xAcosϕ                                  =1-x2A2 sin2ϕy2B2 +x2A2cos2ϕ +sin2ϕ                           -2xYABcos ϕ  =  sin2ϕ    y2B2 +x2A2  -2xyAB  cosϕ= sin2ϕWhen ϕ =π2cosϕ =0  sinϕ = 1y2B2+x2A2  = 1             ....(3)