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A point performs simple harmonic oscillation of period TT and the equation of motion is given by x=asin(ωt+π/6)x = a \sin(\omega t + \pi/6). After the elapse of what fraction of the time period the velocity of the point will be equal to half of its maximum velocity?

A

T/8

B

T/6

C

T/3

D

T/12

Step-by-Step Solution

  1. Identify Velocity Equation: The displacement is x=asin(ωt+π/6)x = a \sin(\omega t + \pi/6). Velocity vv is the time derivative of displacement (v=dx/dtv = dx/dt). v=ddt[asin(ωt+π/6)]=aωcos(ωt+π/6)v = \frac{d}{dt}[a \sin(\omega t + \pi/6)] = a\omega \cos(\omega t + \pi/6)
  2. Identify Maximum Velocity: The maximum value of cos(θ)\cos(\theta) is 1. Therefore, vmax=aωv_{max} = a\omega .
  3. Set Condition: We need the time tt when v=vmax2v = \frac{v_{max}}{2}. aωcos(ωt+π/6)=aω2a\omega \cos(\omega t + \pi/6) = \frac{a\omega}{2} cos(ωt+π/6)=12\cos(\omega t + \pi/6) = \frac{1}{2}
  4. Solve for Time: The general solution for cosθ=1/2\cos \theta = 1/2 is θ=π/3\theta = \pi/3 (for the first positive instance). ωt+π6=π3\omega t + \frac{\pi}{6} = \frac{\pi}{3} ωt=π3π6=π6\omega t = \frac{\pi}{3} - \frac{\pi}{6} = \frac{\pi}{6} Substitute ω=2πT\omega = \frac{2\pi}{T}: 2πTt=π6\frac{2\pi}{T} t = \frac{\pi}{6} t=T12t = \frac{T}{12}
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