Question

A physical balance has its arms of length $60cm$ and $40cm$. What weight kept on pan of longer arm will balance an object of weight $100gf$ kept on other pan?

• A. $33.33gf$
• B. $66.67gf$
• C. $50gf$
• D. $16.67gf$

Answer 1

The correct option is B $66.67gf$

If 100 gf is placed on longer arm then this force will have a perpendicular distance of 40 cm from the centre.
Hence moment of force is $100\times 40=4000gf-cm$.
Hence this must be equal to the weight placed on shorter arm.
Let it be $f$.

$f\times 60=4000$. Hence $f=66.67gf$.