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NEET PHYSICSOscillationsMedium

Question

When two displacements represented by y1=asin(ωt)y_1 = a \sin(\omega t) and y2=bcos(ωt)y_2 = b \cos(\omega t) are superimposed, the motion is:

A

not a simple harmonic

B

simple harmonic with amplitude a/b

C

simple harmonic with amplitude a2+b2\sqrt{a^2+b^2}

D

simple harmonic with amplitude (a+b)/2

Step-by-Step Solution

The superposition of two simple harmonic motions (SHM) with the same angular frequency ω\omega results in a new simple harmonic motion. The resultant displacement yy is the sum of the individual displacements: y=y1+y2=asin(ωt)+bcos(ωt)y = y_1 + y_2 = a \sin(\omega t) + b \cos(\omega t) Using the trigonometric identity cos(ωt)=sin(ωt+π2)\cos(\omega t) = \sin(\omega t + \frac{\pi}{2}), we see that the two waves have a phase difference of ϕ=π2\phi = \frac{\pi}{2}. The resultant amplitude RR for the superposition of two waves with amplitudes aa and bb and phase difference ϕ\phi is given by: R=a2+b2+2abcosϕR = \sqrt{a^2 + b^2 + 2ab \cos\phi} Substituting ϕ=π2\phi = \frac{\pi}{2} (since cosπ2=0\cos \frac{\pi}{2} = 0): R=a2+b2R = \sqrt{a^2 + b^2} Thus, the resulting motion is simple harmonic with an amplitude of a2+b2\sqrt{a^2 + b^2}. This concept is consistent with the principles of phasor addition used in analyzing AC circuits and oscillations .

Exam Context & Concepts Covered

This question aligns with the NEET PHYSICS syllabus, specifically targeting concepts from Oscillations. Mastering this topic is crucial for scoring well in the upcoming medical entrance examinations. Solving conceptually related problems will help you understand the nuances of these concepts and improve your problem-solving speed.

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