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.

1. Draw a diagram of the arrangement showing the fulcrum (F), load (L) and effort (E) with their directions.
2. State the kind of lever.
3. Calculate:
   1. load arm,
   2. effort arm,
   3. mechanical advantage and
   4. the effort needed.

Answer 1

(a)

75 kgf. crow bar

Effort = ?

M.A. = `"L"/"E"`

2 = `("75  kgf")/"E"`

E = `75/2`

E = 37.5 kgf

(b) Class I lever

(c)

1. Load arm 1.5 – 1.0 = 0.5 m
2. Effort arm = 1 m
3. Mechanical advantage = `1.0/0.5 = 2`