So, I was reading a book on mechanics and there I found the following notion about mass. It says that "Experience shows that every body resists any effort to change its velocity,both in magnitude and direction.This property expressing the degree of unsusceptibility of a body to any change in its velocity is inertness and mass is the measure of this inertness."
Now, that is how it describes mass. But the problem which arises is that I'm unable to comprehend what does it mean to resist. Often an example is given wherein a bus suddenly starts moving or stops and we resist any change in velocity by bending in front and something like that. But, the thing here is that we do so because there is friction between our feet and bus floor, and our body is not rigid.
But considering a situation wherein a mass is moving uniformly in space and a force is acted upon it, it doesn't shows any resistance and simply accelerates.
Thinking about it, I've reached a conclusion,which I want you to tell me if its true or not. The conclusion I've drawn is that the body resists any change in its velocity by itself exerting a force (equal and opposite) on the cause of force on it. That is, resistance is basically a manifestation of Newton's third law.
I don't know whether I'm correct or not. So, I request your help. A thing I'd like to mention is that I'm only talking about classical mechanics and want you to be adhered to that as I don't have the required knowledge of quantum mechanics or Einstein's relativity.