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QJEEM22Ph9135: JEE Main 2022 Physics - Class 11 JEEM22Ph9135 Solution: A metre scale is balanced on a knife edge at its centre. When…

A metre scale is balanced on a knife edge at its centre. When two coins, each of mass 10 g are put one on the top of the other at the 10.0 cm mark the scale is found to be balanced at 40.0 cm mark. The mass of the metre scale is found to be x ×\times 10 −- 2 kg. The value of x is ___________.

Step-by-Step Verified Solution

JEE Main 2022 (Online) 24th June Morning Shift Physics - Rotational Motion Question 67 English Explanation
Let M\mathrm{M} be the mass of the meter scale.

The weight Mg\mathrm{Mg} of the scale acts at 50 cm50 \mathrm{~cm} mark.

Finally after putting two coins on the meter scale, balancing the torques about the knife edge, we get,

20g×30=Mg×1020 g \times 30=\mathrm{Mg} \times 10

Mamp;=60 gamp;=60×10−3 kgamp;=6×10−2 kgamp;=x×10−2 kg\begin{aligned}M & =60 \mathrm{~g} \\\\& =60 \times 10^{-3} \mathrm{~kg} \\\\& =6 \times 10^{-2} \mathrm{~kg} \\\\& =x \times 10^{-2} \mathrm{~kg}\end{aligned}

On comparing, we get x=6x=6

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