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.

(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.

(a) Below is the diagram of the crowbar showing the fulcrum (F), load (L) and effort (E) with their directions:

(b) Crowbar belongs to class I lever.

Given,

(i) Total length = 1.5 m

Effort arm = 1 m

$\text{Load arm} = \text{Total length} - \text{Effort arm} \\[0.5em] \text{Load arm} = 1.5m - 1m \\[0.5em] \Rightarrow \text{Load arm} = 0.5 m \\[0.5em]$

(ii) Effort arm = 1 m

(iii)

$\text{Mechanical advantage M.A.} = \dfrac{\text{Effort arm}}{\text{Load arm}} \\[0.5em] M.A. = \dfrac{1}{0.5} \\[0.5em] \Rightarrow M.A. = 2 \\[0.5em]$

(iv) Given,

Load = 75 kgf

We know that,

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

Substituting the values in formula we get,

$\text{Effort} =\dfrac{75}{2} \\[0.5em] \Rightarrow \text{Effort} = 37.5 \text{ kgf} \\[0.5em]$