Question

A uniform meter rule balances horizontally on a knife-edge placed at the 58 cm mark when a weight of 20 gf is suspended from one end.

(i) Draw a diagram of the arrangement.

(ii) What is the weight of the rule?

Answer 1

(i) Diagram:

(ii) Using principle of moments about the 58 cm mark, $W\times (58-50)=20\times (100-58)$

$\Rightarrow W\times 8=20\times 42$

$\therefore W=105gf$