Moment is the rotating effect of a force.
A special case of moment is a couple.
To understand couple, let’s consider a steering
wheel.
We hold the wheel with each hand on two sides
of the wheel and apply force on opposite sides.
Each force creates a moment about the center
of rotation and is equal to the applied force
times the perpendicular distance.
Ideally we want these two forces to be equal
and opposite.
In such a case, sum of these two forces, or
the resultant force will be zero as they are
equal and opposite.
So there is no translation only pure moment.
We call this couple.
So a couple consists of two parallel forces
that are equal in magnitude, opposite in the
sense and do not lie on the same line of action.
Couple is a moment so the unit for couple
is same as the moment
Let us take a look at some examples of couple
in the next video
