Equilibrant and Action-Reaction

In this lecture, we will explain the difference between the two forces of equilibrant and action-reaction, which many people are often confused about.

Neither the equilibrant nor the action-reaction is difficult to understand, so if you don’t think about it too hard, there will be no confusion or anything.
However, it is also true that once you lose track, you are stuck in a negative spiral from which you cannot escape.
Let’s aim for correct understanding.

Find the right pair of forces!

Let’s try an example!

The answers are below, so before you read further, think for yourself first.

Did you get your answer?
The answer is
Equilibrant:1, Reaction:4.

Check out “What force to act!”

Since the equilibrant and the action-reaction are of the same magnitude and opposite directions, it is impossible to distinguish them by magnitude or direction.
You will make a mistake if you do it improperly!

The key to distinguishing between the two is to clarify “what” and “to what” is the force that is acted.

If you write it like this, the difference should be clear.
Once you know the difference, it is easy to tell them apart.

Other concepts that have something in common, such as the equilibrant and the action-reaction relationship, can be complicated for the beginning student.
Be sure to understand them well at the beginning.