Difference between Torque and Couple
Torque and couple are study concepts which most of physics students consider headache because of their confusing concepts. There are many striking similarities and also, stark differences between these two.
Torque is the force behind any rotating object. It can be understood as a twist or turning force which has the capacity to turn an object about an axis. The most basic examples of torque are when you try to unscrew a bolt or nut and when you turn the steering of your car. Students get confused with this simple theory because this force is called torque in school but when they move on to higher studies such as mechanical engineering, it is called moment.
In altogether a different case when applied force vectors add to zero, this force is called a couple, and the joint moment is called a torque. A couple or pure moment can be termed as a rotational force with no moment. The most basic example of couple is when two equal forces act on one thing but do not coincide. Newton-meter is the SI unit of a couple.