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Concepts Of Physics MCQ Edition [Volume 1]
Exam
Concepts Of Physics MCQ Edition [Volume 1]
Subject
Physics
Chapter
Simple Harmonic Motion

Concepts Of Physics MCQ Edition [Volume 1] · Physics · Simple Harmonic Motion

A particle travels in simple harmonic motion described by the...

A particle travels in simple harmonic motion described by the equation x=2.0cos⁡(50πt+tan⁡−10.75)x = 2.0 \cos(50 \pi t + \tan^{-1} 0.75), where xx is in centimetres and tt is in seconds. The motion is initiated at t=0t = 0. At what time does the acceleration attain its maximum magnitude for the first time?

Options

  1. A0.4×10−2 s0.4 \times 10^{-2} \text{ s}
  2. B2.0×10−2 s2.0 \times 10^{-2} \text{ s}
  3. C3.6×10−2 s3.6 \times 10^{-2} \text{ s}
  4. D1.6×10−2 s1.6 \times 10^{-2} \text{ s}

Correct answer

D. 1.6×10−2 s1.6 \times 10^{-2} \text{ s}

Step-by-step solution

The displacement of the particle is given by x=2.0cos⁡(50πt+tan⁡−10.75)x = 2.0 \cos(50 \pi t + \tan^{-1} 0.75).

The acceleration of a particle in simple harmonic motion is a=−ω2xa = -\omega^2 x. The magnitude of acceleration is maximum when the displacement is at its extreme positions, i.e., x=±2.0x = \pm 2.0.

This condition is satisfied when cos⁡(50πt+tan⁡−10.75)=±1\cos(50 \pi t + \tan^{-1} 0.75) = \pm 1.

Let ϕ=tan⁡−1(0.75)=tan⁡−1(34).Theangle\phi = \tan^{-1}(0.75) = \tan^{-1} \left(\dfrac{3}{4}\right). The angle\phiisapproximatelyis approximately37^{\circ} or \dfrac{37\pi}{180} radians.

At t=0t = 0, the phase is ϕ≈37∘\phi \approx 37^{\circ}. The first time the magnitude of acceleration reaches its maximum is when the phase equals π\pi (or 180∘180^{\circ}).

Equating the phase to π\pi:

50πt+ϕ=π50 \pi t + \phi = \pi

50πt=π−ϕ50 \pi t = \pi - \phi

Converting to degrees for simpler calculation:

50×180∘×t=180∘−37∘50 \times 180^{\circ} \times t = 180^{\circ} - 37^{\circ}

9000t=1439000 t = 143

t=t =\dfrac{143}{9000} \approx0.01588 s0.01588 \text{ s}

Rounding to appropriate significant figures, we get t≈1.6×10−2 st \approx 1.6 \times 10^{-2} \text{ s}.
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