What is the Difference Between Torque and Couple?

The main difference between torque and couple lies in the forces involved and their effects on an object. Here are the key differences:

• Torque: Torque is a turning force produced by a single force acting on an object. It is calculated as the force multiplied by the perpendicular distance from the point of application to the axis of rotation. For example, when you use a wrench to tighten a bolt, the force you apply creates a torque that causes the bolt to rotate.
• Couple: A couple is a system of two equal but opposite forces acting on a body, resulting in no net force but a consequent moment. A couple is produced when two forces act on an object with the same magnitude and opposite directions, but do not have the same line of action. For example, when you open a door by pushing on both sides with equal and opposite forces, the door rotates due to the couple created by the combination of the two forces.

In summary:

• Torque is a turning force produced by a single force.
• A couple is a system of two equal but opposite forces acting on a body, resulting in no net force but a consequent moment.

Comparative Table: Torque vs Couple

Here is a table highlighting the differences between torque and couple:

In summary, torque is the turning effect of a single force, while a couple is produced due to two equal and opposite forces acting at a distance. Torque is a vector quantity, whereas the moment of a couple is a free vector. Torque can be expressed as a special case of moment, and they both have different purposes in physics.