The diagram below shows the use of a lever.

(a) State the principle of moments as applied to the above lever.

(b) To which class of lever does it belong? Give an example of this class of lever.

(c) If FA = 10 cm, AB = 490 cm,

calculate:

(i) the mechanical advantage, and

(ii) the minimum effort required to lift the load (= 50N).

(a) The principle of moments states that —

Moment of the load about the fulcrum = Moment of the effort about the fulcrum

(b) The above diagram belongs to Class III lever. The example of Class III lever is a sugar tongs.

(c)

(i) We know that,

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

Given,

Load arm = 490 cm + 10 cm = 500 cm

Effort arm = 10 cm

Substituting the values in the formula we get,

$M.A. = \dfrac{10}{500} \\[0.5em] \Rightarrow M.A. = \dfrac{1}{50} \\[0.5em]$

(ii) We know that,

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

Given,

Load = 50 kgf

Substituting the values in the formula we get,

$\text{Effort} = \dfrac{50}{\dfrac{1}{50}} \\[0.5em] \Rightarrow \text{Effort} = 2500 N \\[0.5em]$