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JEE Main 2023 (25 Jan, Shift 1) · Torque, Couple & Equilibrium of Rigid Bodies

Torque, Couple & Equilibrium of Rigid Bodies question from JEE Main 2023 (25 Jan, Shift 1)

Q17JEE Main 2023 · 25 JAN · SHIFT 1Medium

Torque, Couple & Equilibrium of Rigid Bodies

An object of mass 8 kg is hanging from one end of a uniform rod CD of mass 2 kg and length 1 m pivoted at its end C on a vertical wall as shown in figure. It is supported by a cable AB such that the system is in equilibrium. The tension in the cable is (Take g = 10 m/s22)

Figure

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Answer: (d)

  1. Take torques about the pivot C. The cable at B (CB=0.6CB = 0.6 m) makes 30∘30^\circ with the rod, so its perpendicular part is Tsin⁡30∘T\sin 30^\circ.
  2. Rod weight 2020 N acts at 0.50.5 m; hanging weight 8080 N acts at 11 m.
  3. Tsin⁡30∘×0.6=20×0.5+80×1=90T \sin 30^\circ \times 0.6 = 20 \times 0.5 + 80 \times 1 = 90
  4. 0.3 T=90⇒T=3000.3\,T = 90 \Rightarrow T = 300 N
  5. So the answer is (d) 300 N.
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