Figure shows a uniform metre rule of weight W supported on a fulcrum at the 60 cm mark by applying the effort E at the 90 cm mark.

(a) State with reasons whether the weight W of the rule is greater than, less than or equal to the effort E.

(b) Find the mechanical advantage in an ideal case.

(a) The weight W of the scale is greater than E.

The effort arm is 30 cm and the load arm is 10 cm. In order to balance the scale — weight (W) of scale has to be more than effort (E).

(b) Given,

Load arm = 10 cm
Effort arm = 30 cm

As we know that,

$M.A. = \dfrac{\text{Effort arm}}{\text{Load arm}} \\[0.5em]$

Substituting the values in the formula we get,

$M.A. = \dfrac{\text{30}}{\text{10}} \\[0.5em] \Rightarrow M.A. = 3$