JEE Main 202528 JanuaryEvening Shift

Exam: JEE Main
Year: 2025
Date: 28 January
Shift: Evening Shift
Subject: Physics
Chapter: Center of Mass, Momentum and Collision

JEE Main 2025 · 28 January · Evening Shift · Physics · Center of Mass, Momentum and Collision

A uniform rod of mass 250 g having length 100 cm is balanced on a...

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

Options

A $190\mathrm {~g}$
B $200\mathrm {~g}$
C $300\mathrm {~g}$
D $290\mathrm {~g}$

Correct answer

A. $190\mathrm {~g}$

Step-by-step solution

\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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