Question:

A metre stick is balanced on a knife edge at its centre. When two coins, each of mass $5 \,g$ are put one on top of the other at the $12 \,cm$ mark, the stick is found to be balanced at $45 \,cm$. The mass of the metre stick is

Updated On: Jul 5, 2022
  • $56\,g$
  • $66\,g$
  • $76\,g$
  • $86\,g$
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The Correct Option is B

Solution and Explanation

Let $m$ be the mass of the metre stick concentrated at $C$, the $50 \,cm$ mark as shown in the figure.
In equilibrium, taking moments of forces about $C'$, we get $10 g(45-12) = mg (50-45);$ $10g \times 33 = mg \times 5$ $ m = \frac{10 \times 33}{5} = 66\,g$
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  1. The system of particles refers to the extended body which is considered a rigid body most of the time for simple or easy understanding. A rigid body is a body with a perfectly definite and unchangeable shape.
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