Question

A cook uses a fire tong of length 28 cm to lift a piece of burning coal of mass 250 g. If he applies effort at a distance of 7 cm from the burning coal, what is the effort applied?

Answer 1

A fire tong acts as a third-class lever. The effort is applied between the fulcrum and the load.

Given: Length of tong (fulcrum to load) = load arm = 28 cm

Distance from the load to the effort point = 7 cm

Effort arm = 28 − 7 = 21 cm

Mass of coal = 250 g = 0.25 kg

Taking g = 10 N/kg

Load (L) = mg

= 0.25 × 10

= 2.5 N

Using the principle of moments:

Load × load arm = Effort × effort arm

2.5 × 28 = E × 21

E = `(2.5 × 28)/21`

≈ 3.33 N