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JEE Main 2019 (12 Apr, Shift 1) · Rotational Kinematics & Dynamics

Rotational Kinematics & Dynamics question from JEE Main 2019 (12 Apr, Shift 1)

Q62JEE Main 2019 · 12 APR · SHIFT 1Difficult

Rotational Kinematics & Dynamics

A uniform rod of length ℓ\ell is being rotated in a horizontal plane with a constant angular speed about an axis passing through one of its ends. If the tension generated in the rod due to rotation is T(x) at a distance x from the axis, then which of the following graphs depicts it most closely?

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Answer: (b)

  1. Tension at xx provides centripetal force for the part from xx to ℓ\ell: T(x)=∫xℓmℓω2s dsT(x) = \int_x^{\ell}\dfrac{m}{\ell}\omega^2 s\,ds.
  2. T(x)=mω22ℓ(ℓ2−x2)T(x) = \dfrac{m\omega^2}{2\ell}(\ell^2 - x^2): a downward parabola, maximum at x=0x = 0 with zero slope, zero at x=ℓx = \ell.
  3. This matches graph (b).
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