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JEE Main 2018 (15 Apr, Shift 1) · Torque, Couple & Equilibrium of Rigid Bodies

Torque, Couple & Equilibrium of Rigid Bodies question from JEE Main 2018 (15 Apr, Shift 1)

Q38JEE Main 2018 · 15 APR · SHIFT 1Medium

Torque, Couple & Equilibrium of Rigid Bodies

Figure

A uniform rod ABAB is suspended from a point X,X, at a variable distance xx from AA, as shown. To make the rod horizontal, a mass mm is suspended from its end A.A. A set of (m,x)(m, x) values is recorded. The appropriate variables that give a straight line, when plotted, are:

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Answer: (b)

  1. Let the rod have mass MM and length LL; its weight acts at L/2L/2 from A.
  2. Moments about X: mg x=Mg(L2−x)mg\,x = Mg\left(\frac{L}{2} - x\right)
  3. m=ML2⋅1x−Mm = \frac{ML}{2}\cdot\frac{1}{x} - M, a straight line between mm and 1x\frac{1}{x}.
  4. So the answer is (b) m,1xm, \frac{1}{x}.
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