Question

A man uses a crowbar of length 1.5m to raise a load of 75 kgf by putting a sharp edge below the bar at a distance of 1m from his hand. (a) Draw a diagram of the arrangement showing the fulcrum (F), load (L) and effort (E) with their directions. (b) State the kind of lever. (c) Calculate (i) load arm, (ii) effort arm, (iii) mechanical advantage, and (iv) the effort needed.

Answer 1

Crowbar is a class I lever.

(i) Total length of crowbar = 1.5 m

Effort arm = 1 m

Load arm = 1.5 - 1 = 0.5 m

(ii) Effort arm = 1 m

(iii) Mechanical advantage $=\frac{Effortarm}{Loadarm}=\frac{1}{0.5}=2$

(iv) the effort needed,

Effort $=\frac{Load}{Mechanicaladvantage}=\frac{75}{2}=37.5kgf$