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Q.Define simple harmonic motion. Obtain an expression for the velocity and acceleration of SHM.

Nagaland NbseNagaland Board of School Education (Class XI) 2022Subjective· 3mImportance★★★★★
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In SHM, v=ωA2−x2v=\omega\sqrt{A^2-x^2} and a=−ω2xa=-\omega^2x — acceleration is always proportional to displacement, directed toward the mean position.

Definition: Simple harmonic motion (SHM) is a type of periodic motion in which the restoring force (and hence the acceleration) acting on the particle is directly proportional to its displacement from a fixed mean (equilibrium) position, and is always directed towards that mean position:

F=−kxor equivalentlya=−ω2xF = -kx \quad\text{or equivalently}\quad a = -\omega^2 x

where ω\omega is the angular frequency, related to kk and mass mm by ω=k/m\omega=\sqrt{k/m}.

Displacement: The general solution for the displacement of a particle in SHM is

x(t)=Asin⁡(ωt+ϕ)x(t) = A\sin(\omega t + \phi)

where AA is the amplitude and ϕ\phi is the initial phase.

Velocity: Differentiating x(t)x(t) with respect to time,

v=dxdt=Aωcos⁡(ωt+ϕ)v = \frac{dx}{dt} = A\omega\cos(\omega t+\phi)

Using cos⁡2θ=1−sin⁡2θ\cos^2\theta = 1-\sin^2\theta and sin⁡(ωt+ϕ)=x/A\sin(\omega t+\phi) = x/A:

v=Aω1−sin⁡2(ωt+ϕ)=ωA2−x2v = A\omega\sqrt{1-\sin^2(\omega t+\phi)} = \omega\sqrt{A^2 - x^2} …

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