Question

A uniform metre rule balances ho rizontally on a knife edge placed at the $58cm$ mark when a weigh of $29gf$ is suspended from one end.
(i)Draw a diagram of the arrangement
(ii)What is the weight of the rule?

Answer 1

(ii) The center of gravity of a uniform half meter rule is 25 cm.

The rule balances horizontally on a knife edge at 29 cm mark when a weight of 20 kgf is suspended from one end.

The difference in the center of gravity and the point of balance$=29-25=4cm\left(Y\right)$

The weight is suspended at one of the extremes,

Let us assume at the 50 cm end.

Therefore, the distance from the point of knife edge to the weight $=50-29=21cm\left(X\right)$

Weight of meter rule $=\frac{X}{Y}\times Suspendedweight$

$\therefore$ Weight of meter rule $=\frac{21}{4}\times 20=105kgf$