Suppose two equal and opposite forces F act tangentially to a wheel W, and rotate it through an angle θ (Figure).

Then, the work done by each force = Force x distance = F x r

(since r θ is the distance moved by a point on the rim)

Total work done **W = F r θ +F r θ = 2 Fr θ**

but torque τ = F x 2r = 2 F r

so, work done by the couple, **W = τθ**

**Examples of couple are**

- Forces applied to the handle of a screw press,
- Opening or closing a water tap.
- Turning the cap of a pen.
- Steering a car.