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OccultHawk 08-24-2019 10:07 PM

Quote:

Originally Posted by Pet_Sounds (Post 2074493)
Time is what a clock measures.

Couldn’t an extraordinarily precise clock measure the amount of time a ball in mid air isn’t moving so therefore if physicists wanted to describe it as such it could be called at rest same as me sitting on a sofa because it’s just a matter of time before my body weight is going to win out even though at the moment the forces are (almost) equal not allowing me to fall through?

Pet_Sounds 08-24-2019 10:11 PM

Quote:

Originally Posted by OccultHawk (Post 2074495)
Couldn’t an extraordinarily precise clock measure the amount of time a ball in mid air isn’t moving so therefore if physicists wanted to describe it as such it could be called at rest same as me sitting on a sofa because it’s just a matter of time before my body weight is going to win out even though at the moment the forces are (almost) equal not allowing me to fall through?

No, no matter how small your interval of measure is the ball in midair will always exhibit some movement in that interval.

EDIT: To be clear, we're talking about Newtonian physics here.

The Batlord 08-24-2019 10:16 PM

Quote:

Originally Posted by Pet_Sounds (Post 2074490)
Yeah, there's a difference in equations. Calculus was invented basically for this question. You need an "open interval" (which can be arbitrarily small) of time around a given point to discuss instantaneous rate of change, and the difference comes down to the behaviour of the object in that open interval as it approaches the point you're interested in. In the case of the ball in mid-air, its motion changes immediately before and after the point in time at which its velocity is zero; the ball on the ground doesn't move at all.

Sorry I'm not explaining this very well, it's hard without math.

So the "point of non-zero acceleration" is simply a point in whatever relevant bigger equation that relates to the equation that describes the behavior of the object before the "point of non-zero acceleration" and how that relates to the equation describing the behavior of the object after the "point of non-zero acceleration"? [i.e. the ball was thrown (before point of non-zero acceleration), the ball reached its height (point of non-zero acceleration), and the ball fell (after point of non-zero acceleration)].

That sounds like a truism to me, and if that's correct is there an equation or "family" of equations or whatever to describe that "point of non-zero acceleration" or is that point simply a plot to point in the greater equation? Like that point of non-zero acceleration is constant no matter the equation and does not have to be calculated, or the nature of the greater equation of the "rise and fall of the ball" will dictate what the point of non-zero acceleration will be?

Quote:

Originally Posted by Pet_Sounds (Post 2074493)
Time is what a clock measures.

But I mean time is a thing we as humans can not measure because we do not have an organ to measure it realistically, in the same way that we use an imperfect two dimensional measuring organ (the eye) to measure three dimensional space. It's not perfect, does not make any sense as a measuring instrument if you look at its performance too closely, but it's good enough for government work. The brain measures time by memory and does so imperfectly but it works as well as we can hope. A clock measures time but we use the brain to interpret what that measurement means and we do it imperfectly which is why we need math to fix our ****.

It sounds to me that this calculus equation you're talking about with nonzero acceleration is our way of breaking down time in relation to a certain instance of movement in a way that makes it make sense in as best a way as we can.

The Batlord 08-24-2019 10:21 PM

Quote:

Originally Posted by elphenor (Post 2074499)
nerds

shut up, goth boy

Pet_Sounds 08-24-2019 10:22 PM

Quote:

Originally Posted by Doug McClasky (Post 2074500)
So the "point of non-zero acceleration" is simply a point in whatever relevant bigger equation that relates to the equation that describes the behavior of the object before the "point of non-zero acceleration" and how that relates to the equation describing the behavior of the object after the "point of non-zero acceleration"?

That sounds like a truism to me, and if that's correct is there an equation or "family" of equations or whatever to describe that "point of non-zero acceleration" or is that point simply a plot to point in the greater equation?

In this case, position is given by a quadratic equation in one variable (i.e. a parabola) velocity is given by its first derivative (i.e. a possibly sloped straight line) and acceleration is given by its second derivative (i.e. a level straight line).

Quote:

Originally Posted by Doug McClasky (Post 2074500)
It sounds to me that this calculus equation you're talking about with nonzero acceleration is our way of breaking down time in relation to a certain instance of movement in a way that makes it make sense in as best a way as we can.

Yeah, it's a model developed by Newton.

OccultHawk 08-24-2019 10:25 PM

Quote:

Originally Posted by Pet_Sounds (Post 2074498)
No, no matter how small your interval of measure is the ball in midair will always exhibit some movement in that interval.

EDIT: To be clear, we're talking about Newtonian physics here.

ok

I think (know actually) everything is either moving toward or away from the center of the earth just far more slowly than the midair ball. That’s an example of how philosophy and language informs science.

OccultHawk 08-24-2019 11:06 PM

Quote:

In this case, position is given by a quadratic equation in one variable (i.e. a parabola) velocity is given by its first derivative (i.e. a possibly sloped straight line) and acceleration is given by its second derivative (i.e. a level straight line).
https://qph.fs.quoracdn.net/main-qim...fec3ded33716ab

https://bam.files.bbci.co.uk/bam/liv.../zgtd6yc/small

Are these examples?

If not can you find a graph?

Pet_Sounds 08-24-2019 11:22 PM

1 Attachment(s)
These are equations for a ball thrown vertically into the air at 5.0 m/s. Position is purple, velocity is green, and acceleration is blue. The x-axis is time. Ignore the bits where the parabola lies below the x-axis; they're not relevant for this example.

The first few Khan Academy videos on physics probably explain this way better than I can.

OccultHawk 08-24-2019 11:28 PM

I loved KA when I had a computer but it sucks on a phone.

When I had a computer I had tons of badges and ****.

Then they changed from stars to leaves or something and my computer died.

BassoonPlatoon 08-25-2019 12:34 AM

Quote:

Originally Posted by Pet_Sounds (Post 2074517)
These are equations for a ball thrown vertically into the air at 5.0 m/s.

I did not expect things to launch off like this based on a one sentence blurb of mine that was about 1 minute or 2 of real time. Thanks for taking such an interest, as well as for mentioning Khan Academy it's a useful tool for the individual trying to teach themselves, and their are plenty of ways online to do it in addition.

Anyway, to see if I can add anything here, position of an object is usually always nonzero if you add in the Earth's rotation. I forgot about the forces of gravity when talking about the parked car example so thanks for reminding me about that, kind of a lot more factors of physics to consider than I realized at first, without even mentioning the different subsets.


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