(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 = 10cm, AB = 490cm, calculate: (i) the mechanical advantage, and (ii) the minimum effort required to lift the load (= 50N).

Solutions:

(a) Using the principle of moments,

Moment of the load about the fulcrum is equal to the moment of the effort about the fulcrum. therefore, we have –

Load × FB = Effort × FA

(b) It belongs to Class III lever and example of this lever is a knife.

(c) According to the question ,

FA is 10 cm

AB is 490 cm

Therefore, BF = 490 + 10 = 500 cm

Expression for the mechanical advantage is

M.A. = AF / BF = 10 / 500

M.A. = 1 / 50

The minimum effort required to lift the load is given the following expression –

Effort = Load / M.A = 50 / 1 / 50

Effort = 2500 N