A bicycle can be steered by applying a pair of equal but opposite forces to the handlebars, which act as a lever - Leaving Cert Physics - Question a - 2015

The turning effect of a force is called moment or torque. It can be defined as the product of the force and the perpendicular distance from the line of action of the force to the pivot point.

A pair of equal but opposite forces is referred to as a couple. This configuration produces rotation without translation, as the forces cancel each other out.

Given that the distance between the cyclist's hands is 40 cm (0.4 m) and each hand applies a force of 20 N, we can calculate the moment (M) as follows:

$M = F imes d$

Where:

• F is the total force applied, taking into account both hands: $F = 20 ext{ N} + 20 ext{ N} = 40 ext{ N}$
• d is the distance: $d = 0.4 ext{ m}$

Substituting the values, we get:

$M = 40 ext{ N} imes 0.4 ext{ m} = 16 ext{ Nm}$

Thus, the turning effect of the force is 16 Nm.