A thing I want to know about inertia and derivatives of acceleration

[SilentSky23]

Well, I just had this thought some time ago, and I am curious about it. I would like to know if it is actually true or not.

So, we all know about inertia, right? The resistance to acceleration, or change in motion. Well, there is also a concept about derivatives of acceleration, mainly jerk and yank. If you don't know, jerk is said to be the rate of change in acceleration, and yank a rate of change in force. Now, about inertia, here is the thought in question.

If inertia resists acceleration, and therefore reduces it when a force is applied to something, would inertia not actually act as a yank, and thus jerk to acceleration, and thus reduce it when a force is applied? I mean, I know I could be wrong, which is why I even ask. I know that inertia is a property of matter, which is equal to mass, not a force in itself,  and by extension, not even a yank. Maybe it is a property that provides yank, and thus jerk to acceleration somehow as the resistance to change in motion? Kinda like how friction, even though it is a force unlike inertia, resists motion and slows it down? Also, inertia is equal to mass, which is a measure of how much matter there is in something, and if I recall correctly, mass is needed to exert a force on things.

I am not saying I am right on my thought, which is why this is more of a question if anything. So correct me if I am wrong, but would inertia act as or provide a yank, and thus a jerk to acceleration when  a force is applied to something?

[swansont]

Inertia is a concept: the tendency for an object to be at rest, or motion to be uniform, in the absence of a force. This can also be thought if as resistance to acceleration in a lot of situations. Thus it can be mass or it can be momentum (since F = dp/dt)

To say inertia reduces the acceleration of an object isn't right. Inertia isn't a force. The acceleration is what it is, according to F = ma (for a system with constant mass). There's no second term; we don't have a variable for inertia in our equations. To say that this reduces the acceleration is sort of double-counting.

 

 

 

[SilentSky23]

6 minutes ago, swansont said:

Inertia is a concept: the tendency for an object to be at rest, or motion to be uniform, in the absence of a force. This can also be thought if as resistance to acceleration in a lot of situations. Thus it can be mass or it can be momentum (since F = dp/dt)

To say inertia reduces the acceleration of an object isn't right. Inertia isn't a force. The acceleration is what it is, according to F = ma (for a system with constant mass). There's no second term; we don't have a variable for inertia in our equations. To say that this reduces the acceleration is sort of double-counting.

 

 

 

I see. I kinda meant by inertia reducing acceleration, I meant by resisting it. What do you mean by double counting, anyway?

Either way, I figured there was something wrong with what I thought. Perhaps I didn't think hard enough on this, or just focused on one or a few things alone. Thanks so much.

Though to clarify, I only said reducing because of the equation, force equals mass times acceleration. As I recall, when force increases, acceleration increases, but when mass increases, the acceleration decreases due to resistance, and the more force is needed to accelerate something. Maybe I had something wrong there, too?

[swansont]

16 minutes ago, SilentSky23 said:

I see. I kinda meant by inertia reducing acceleration, I meant by resisting it. What do you mean by double counting, anyway?

To me "If inertia resists acceleration, and therefore reduces it when a force is applied to something" implies the acceleration is somehow even smaller than a = F/m because the mass is resisting acceleration, or that it would be bigger than that if mass didn't resist acceleration. But a= F/m is what is meant by mass being resistance to acceleration. For a given force, the acceleration scales inversely with the mass.   

 

 

16 minutes ago, SilentSky23 said:

 Though to clarify, I only said reducing because of the equation, force equals mass times acceleration. As I recall, when force increases, acceleration increases, but when mass increases, the acceleration decreases due to resistance, and the more force is needed to accelerate something. Maybe I had something wrong there, too?

No, that seems right. But I think here is an example of why we use math to express what's going on, because it has far less ambiguity than the language we use for prose and poetry.

[Bufofrog]

16 minutes ago, SilentSky23 said:

As I recall, when force increases, acceleration increases, but when mass increases, the acceleration decreases due to resistance, and the more force is needed to accelerate something.

F=ma

An increase in the force means that the acceleration increased or the mass increased or both increased.

A decrease in the force means that the acceleration decreased or the mass decreased or both decreased.

 

 

[SilentSky23]

7 minutes ago, swansont said:

To me "If inertia resists acceleration, and therefore reduces it when a force is applied to something" implies the acceleration is somehow even smaller than a = F/m because the mass is resisting acceleration, or that it would be bigger than that if mass didn't resist acceleration. But a= F/m is what is meant by mass being resistance to acceleration. For a given force, the acceleration scales inversely with the mass.   

 

 

No, that seems right. But I think here is an example of why we use math to express what's going on, because it has far less ambiguity than the language we use for prose and poetry.

I see, I must have read sayings in the wrong places, then. But, just so it is clear to me, how is resisting acceleration different from reducing it, exactly? Just want to make sure.

7 minutes ago, Bufofrog said:

F=ma

An increase in the force means that the acceleration increased or the mass increased or both increased.

A decrease in the force means that the acceleration decreased or the mass decreased or both decreased.

 

 

Man, I forgot about those two for some reason. I guess it is what is in the formula that matters, if you know what I mean, or how the formula works. I knew there was a potential reason why my thought was possibly wrong, and I only wanted to check on that. Looks like I found the reason, thanks to what you said.

To both of you, I hope you did not mind me asking this, especially since there are some things I happened to accidentally miss.

Edited November 15, 2019 by SilentSky23

[Bufofrog]

3 hours ago, SilentSky23 said:

I hope you did not mind me asking this

I am sure everyone on this forum would encourage you to ask questions and learn more.

[swansont]

20 hours ago, SilentSky23 said:

I see, I must have read sayings in the wrong places, then. But, just so it is clear to me, how is resisting acceleration different from reducing it, exactly? Just want to make sure.

To reduce implies a change from one value to another. But that's not what's happening. Mass doesn't change the acceleration. It tells you what the acceleration will be. F = ma. Nothing has changed. Nothing has been reduced.

Changing the mass changes the acceleration.

Again, this is an issue of semantics that (largely) goes away when you look at the equation.

 

 

[SilentSky23]

3 hours ago, swansont said:

To reduce implies a change from one value to another. But that's not what's happening. Mass doesn't change the acceleration. It tells you what the acceleration will be. F = ma. Nothing has changed. Nothing has been reduced.

Changing the mass changes the acceleration.

Again, this is an issue of semantics that (largely) goes away when you look at the equation.

 

 

So you are saying it is both increasing and decreasing the acceleration, depending on how mass is changed?

I guess I misused the word "reduced", as I only talked about what happens to acceleration when mass increases. I did not include what happens when mass decreases. My bad. That said, I could go back and say inertia could provide a yank and thus jerk for acceleration, keyword, could. However, if I understand inertia being a resistance, even if I say that the resistance somehow provides a yank, I doubt that inertia being a yank is the case very much. I mean, inertia is not just a property, but a law, a tendency, is it not? Anything else I am missing?

Edited November 16, 2019 by SilentSky23

[swansont]

Newton’s first law is the law of inertia