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JEE Mains · Physics · STD 11 - 6. system of particles and rotational motion

A uniform rod of mass 250 g having length 100 cm is balanced on a sharp edge at 40 cm mark. A mass of 400 g is suspended at 10 cm mark. To maintain the balance of the rod, the mass to be suspended at 90 cm mark, is

  1. A \(190\mathrm {~g}\)
  2. B \(200\mathrm {~g}\)
  3. C \(300\mathrm {~g}\)
  4. D \(290\mathrm {~g}\)
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Answer & Solution

Correct Answer

(A) \(190\mathrm {~g}\)

Step-by-step Solution

Detailed explanation

\(\begin{aligned} & \tau_{\text {Net }}=0 \Rightarrow(400 \mathrm{~g} \times 30)=(250 \mathrm{~g} \times 10)(\mathrm{mg} \times 50) \\ & \mathrm{m}=\frac{12000-2500}{50}=\frac{9500}{50} \\ & \mathrm{M}=190 \mathrm{~g}\end{aligned}\)
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