Torque is a twisting or turning force about an axis, that can be applied in a clockwise or counter-clockwise direction. A good example of this is a vehicle steering mechanism; to turn a corner the driver applies a force to the steering wheel which applies torque directly to the steering column. This torque is generated by a combination of the force from the driver’s hands and distance the hands are from the centre of the wheel.
Torque is a function of force and length (known as the moment or moment arm), this is shown below in our simple ‘seesaw’ diagram. The seesaw is balanced even though the forces applied to each side are different, this is because the torque at the middle point is the same. The calculations are as follows:
Left Side = 100N force x 1 metre = 100Nm of torque
Right Side = 300N force x 1/3 metre = 100Nm of torque
The most common metric engineering units for torque is the Newton metre (Nm), whilst the most common imperial engineering units is foot pounds (ft.lb).