Question

A man uses a crowbar of length 1.5 m to raise a load of 75 kgf by putting a sharp edge below the bar at a distance 1 m from his hand. Draw a diagram of the arrangement showing the fulcrum (F), load (L) and effort (E) with their directions, State the kind of lever. 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 $=1.5m$

Effort arm $=1m$

Load arm $=1.5-1=0.5m$

(ii) Effort arm $=1m$

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

(iv) The effort needed

$Effort=\frac{Load}{M.A.}=\frac{75}{2}=37.5kgf$