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NEET 2021 · Torque, Couple & Equilibrium of Rigid Bodies

Torque, Couple & Equilibrium of Rigid Bodies question from NEET 2021

Q25NEET 2021Medium

Torque, Couple & Equilibrium of Rigid Bodies

A uniform rod of length 200 cm and mass 500 g is balanced on a wedge placed at 40 cm mark. A mass of 2 kg is suspended from the rod at 20 cm and another unknown mass 'm' is suspended from the rod at 160 cm mark as shown in the figure. Find the value of 'm' such that the rod is in equilibrium. (g = 10 m/s2)

Figure

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Answer: (a)

  1. Moments about the wedge at 40 cm; the rod's weight acts at its centre, 100 cm.
  2. Anticlockwise: 2×(40−20)=402\times(40-20) = 40 kg cm
  3. Clockwise: 0.5×(100−40)+m(160−40)=30+120m0.5\times(100-40) + m(160-40) = 30 + 120m
  4. 40=30+120m⇒m=11240 = 30 + 120m \Rightarrow m = \frac{1}{12} kg, so the answer is (a).
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