# SilentSky23

Senior Members

49

1. ## Question about axis of rotation and center of gravity

No need to say sorry. I say I need to say that for not articulating the question well enough in the first place.
2. ## Question about axis of rotation and center of gravity

I will try next time. And no.
3. ## Question about axis of rotation and center of gravity

That should do, and if it didn’t, close enough. Thanks.
4. ## Question about axis of rotation and center of gravity

Sorry. I forgot to use center of gravity, and I did not understand how complex this was. For examples, what about a gymnast doing, well, a back flip or another gymnastics routine if that counts? That was mainly what I was going for, anyway. Also, forget center of gravity. Let's use center of mass for the question I was asking, instead.
5. ## Question about axis of rotation and center of gravity

What I was after was if anything rotation based in physics, like moment of inertia and such, is connected to center of gravity, to the point that anything rotation based changes when the center of mass changes. Like if the center of gravity is outside the body, mainly a non-rigid body, does anything like moment of inertia change as in become easier or harder. Why would it be hard to understand?
6. ## Question about axis of rotation and center of gravity

My bad, I should have known that not all rotations act through the center of mass, something I learned by looking up before you made this post. I should have thought this more carefully before I made this topic. Maybe I was not talking about axis of rotation, but maybe moment of inertia? If moment of inertia has anything to do with center of gravity, does moment of inertia change when the center of gravity changes? Either way, I am interested in the part of your post I bolded. Can you please tell me more, if you can?
7. ## Question about axis of rotation and center of gravity

Isn't the external force just the cause of rotation, though? Rather than the line acting through a point in the body? I thought those were two different things. The line part was what I meant by axis of rotation.
8. ## Question about axis of rotation and center of gravity

Yeah, I wasn't really talking about external forces here.
9. ## Question about axis of rotation and center of gravity

I only said the through the center of gravity part because I kept reading that online and in books. At least for the human body int he pelvic area. Maybe I phrased it wrong, and meant intersect at the center of gravity? If that means anything? Or is the line through the center of gravity?
10. ## Question about axis of rotation and center of gravity

Now, if I am not mistaken, from what I know, the axis of rotation of a body usually goes through the center of gravity of a body. Also, the position of the center of gravity, if I recall correctly, does change when the position of the body of the living being or object in question changes. Well, just to make sure, I must ask: would the location of the axis of rotation change if the position of the center of gravity changes as well?
11. ## Question about same accelerations

To be honest, being told which would stop first; that is actually all I need.
12. ## Question about same accelerations

So, are you expecting numbers? I am kinda having trouble understanding what you want from me when talking about this situation. If surface level and air resistance and such aren't going to be enough here as it may seem, tell me, what should I tell you, especially for next time when I do ask something like this, just to be safe?
13. ## Question about same accelerations

I did say the type of surface, which is wooden. Not to mention smooth. As for the other things, say the air resistance is normal, or the usual amount in everyday life (nothing too strong) with no wind, and the level of the surface is, well, flat. Anything else you need to know?
14. ## Question about same accelerations

Well, what I meant in my initial saying was that I believe lighter objects accelerate faster and go farther than the ones with more mass, under the same exerted force, of course. Now, for a light object and a heavy object going at the same acceleration, under different forces acting on each of them; assuming the forces are both different in magnitude but acting in the same amount of time; with resisting forces like friction being the same on both objects in terms of magnitude, but acting for a longer time than the two forces that accelerated the objects in the first place, which one would come to a stop sooner than the other if one has the higher inertia than the other? How is this? EDIT: For the surface, say the surface is a wooden floor in a house.
15. ## Question about same accelerations

Yeah, I know, I was going to edit that part about acceleration, but I see I can't now. Still, say that the lighter object is exerted for less than a second, and the second object has a bigger force around the same amount of time. For the negative acceleration from the resistance that eventually stops them, I am not sure. Would the times of negative acceleration be different for each of them?
16. ## Question about same accelerations

But by inertia, wouldn't the lighter object stop sooner, since it has less resistance to change in its velocity?
17. ## Question about same accelerations

I wanted to make sure of something here. Now, I believe it is the case when an object with lighter mass, or inertia, will travel faster and farther than one with a heavier mass or inertia under the same force. Now, consider an object that is light and one that is heavy, both going at the same acceleration, but with different forces acting, and they start moving across either the ground or the air, depending on where they are when a force acts on them. Now, with the same acceleration, which object will go farther before stopping, with either friction, air resistance, or a force exerted by something or someone that is the same force for both objects?
18. ## Negative Mass and Negative Inertia

I have a question. Before I start, I want to say that I know negative mass itself has not been observed or proven to exist, if it does at all. That is why this is more of a what-if question if that is okay. Anyway... Say an object has negative mass and therefore negative inertia. Now, considering inertial reference frames, or fictitious forces, objects with normal mass appear to move, such as going backwards seemingly when say, a car it is in speeds up. If a negative mass object were to exist, and were place inside the car before it speeds up, would the object appear to go the opposite direction of what a normal mass object would do when that car moves, as in that negative mass apparently going forward rather than backward when the car speeds up? As well as going backward apparently instead of forward when a car slows down, if I have inertial reference frames down correctly? All due to fictitious forces? Or would it be the same as normal, positive inertia? I know this seems rather outlandish, possibly even for a hypothetical question in physics, but I have been thinking about it and I am rather curious. I hope nothing bad happens by asking this. So, is there anything to say about this question, if there is something?

Alright, I now get it. Thanks.

More like a hand pushing against a wall, if that counts.

Applied or normal force, to be exact.

May I ask why that is the case? Do you mean they can't or, there is just no knowledge of what happens? Let me ask another question: Does mass, not infinite, of course, exert contact forces at all, or does it not?

What about non-gravitational forces? Like applied forces or other contact forces?

And that question is... Would a moving object with infinite mass exert an infinite force on other objects? If so, why? If not, why not?
25. ## A thing I want to know about inertia and derivatives of acceleration

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?
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