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NEET PHYSICSEasy

If a body is executing simple harmonic motion with frequency nn, then the frequency of its potential energy is:

A

3n3n

B

4n4n

C

nn

D

2n2n

Step-by-Step Solution

  1. Displacement Equation: For a body executing Simple Harmonic Motion (SHM) with frequency nn, the angular frequency is ω=2πn\omega = 2\pi n. The displacement xx varies with time tt as x=Asin(ωt)x = A \sin(\omega t) (or a cosine function).
  2. Potential Energy Formula: The potential energy (UU) of the oscillator is given by U=12kx2U = \frac{1}{2}kx^2, where kk is the force constant.
  3. Substitution and Trigonometric Identity: Substituting the displacement equation: U=12k(Asin(ωt))2=12kA2sin2(ωt)U = \frac{1}{2}k (A \sin(\omega t))^2 = \frac{1}{2}kA^2 \sin^2(\omega t) Using the trigonometric identity sin2θ=1cos(2θ)2\sin^2 \theta = \frac{1 - \cos(2\theta)}{2}: U=12kA2[1cos(2ωt)2]=14kA214kA2cos(2ωt)U = \frac{1}{2}kA^2 \left[ \frac{1 - \cos(2\omega t)}{2} \right] = \frac{1}{4}kA^2 - \frac{1}{4}kA^2 \cos(2\omega t)
  4. Frequency Analysis: The term cos(2ωt)\cos(2\omega t) indicates that the potential energy oscillates with an angular frequency of 2ω2\omega. Since frequency is proportional to angular frequency (f=Ω2πf = \frac{\Omega}{2\pi}), the frequency of the potential energy is 2n2n.
  5. Conclusion: Both kinetic and potential energies in SHM vary periodically with double the frequency of the displacement (2n2n), although the total energy remains constant.
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