Question

A uniform metre rule of mass $100g$ is balanced on a fulcrum at mark $40cm$ by suspending an unknown mass $m$ at the mark $20cm$. It can be balanced by another mass of $X$ by suspending at the mark $50cm$. Find X.

• A. $50$
• B. $60$
• C. $100$
• D. $25$

Answer 1

Answer: (A)

$50$

Let x be the point where 100g of weight is suspended Anti clock wise moment $=m\ast 20$

Clock wise moment $=100\ast (50-40)=1000$

by the law of moments

clock wise moments = anticlock wise moments

$20m=1000$

$m=50g$