Question

A crowbar of length 120 cm has its fulcrum situated at a distance of 20 cm from the load. Calculate the mechanical advantage of the crowbar.

Answer 1

Total length of crowbar = 120 cm

Load arm = 20 cm

Effort arm = 120 − 20 = 100 cm

Mechanical advantage M.A. = `"Effort arm"/"Load arm"`

M.A. =` 100/20=5`

Answer 2

By the principle of moments.

Moments of load about the fulcrum = Moment of efforts about the fulcrum

We have: W × 20 = P × (120 − 20)

`"W"/"P"=100/20`

= 5.