Here we go again.

It's the differene between the position at two times divided by the time elapsed between the two positions. — Philofile

That's average velocity. The instantaneous velocity is the slope of the tangent of the position-time graph at that particular instant of time, dx/dt.

But that will not convince some folk because they didn't do enough maths at school.

A differential is a difference too.

Position = Measurement of space
Time = Measurement of time
Velocity = Measurement of motion

If there is no motion, even over an infinite period of time there is no change in position.

Velocity is measurement of two positions. The positions of particles change. But that goes hand in hand with two different times. But which of the two is fundamental?

I've given you the answer. What you do with it is up to you.

Velocity is measurement of two positions. The positions of particles change. But that goes hand in hand with two different times. But which of the two is fundamental? — Philofile

How does the position of a particle change?

I've given you the answer. What you do with it is up to you. — Banno

I could have given that answer myself. Every velocity is an average one.

How does the position of a particle change? — Hermeticus

It depends on the force acting on it.

So what's difference between speed and velocity? If I run around in a circle at 10m/sec what's my speed, average velocity, and my instantaneous velocity at t₀?

So what's difference between speed and velocity — magritte

Speed is magnitude. Velocity is magnitude and direction. Scalar and vector.

I'm moving in a car (I have a velocity). I move (in my car) from New York to San Francisco. If I weren't moving (had a velocity) at all points between New York and San Francisco, how the hell did I reach San Francisco? :chin:

By moving. But at no point you had a velocity. That's defined by us. Compare it with physics without time...

By moving. But at no point you had a velocity. That's defined by us. Compare it with physics without time... — Philofile

But time is consumed in the journey. My watch and my calender says so.

Also, explain this: a person X and Y are racing each other in a 100 m dash. X wins the race i.e. X and Y can be ordered in a sequence, X first, Y second. This ordering is not spatial, both ran 100 m. In what sense can you say that X is first and Y second? Time! Velocity then is a true physical quantity.

But time is consumed in the journey. My watch and my calender says so. — TheMadFool

That's exactly what my question is about. Can you remember that jewish guy in English parlament smashing his wristwatch?

Every velocity is an average one. — Philofile

Your efforts are wasted on Banno. Some people think they know everything and refuse to learn anything.

To address your op, there is no such thing as a "physical quantity". "Physical" means of the body, where a body is a thing, or object. A quantity may be of one, or a multitude of objects. That's why quantity is an abstraction, or universal, and not something physical

Some people think they know everything and refuse to learn anything. — Metaphysician Undercover

Indeed, on this we agree, but it seems we disagree as to who...

Your inevitable presence here doubtless assures that this thread will have a long and unproductive continuation.

To address your op, there is no such thing as a "physical quantity". — Metaphysician Undercover

Can't a body, or matter, have quantities? Mass, charge, position, maybe velocity?

That's exactly what my question is about. Can you remember that jewish guy in English parlament smashing his wristwatch? — Philofile

Perhaps he was onto something.

Men talk of killing time, while time quietly kills them. — Dion Boucicault

:grin:

Jokes aside, timelessness is not something I have the wherewithal to tackle at the moment. I tried turning it over in my mind and I must admit I can't even parse the claim that time is an illusion. What does that even mean?

time is an illusion. What does that even mean? — TheMadFool

That we invented it. It's no illusion. It's very real. But Einsteins spacetime grant Nature to much.

Can't a body, or matter, have quantities? Mass, charge, position, maybe velocity? — Philofile

These are all things we assign to the body, in predication. We might say that the body has something real, a property which corresponds to the concept assigned, but that all depends on the accuracy of the concept, in its capacity for modeling reality. That's why Banno's "instantaneous velocity" is a bad conception, when judged for truthfulness. Though it is a very useful concept, it's obvious that there is nothing real which corresponds with it.

"Mass" is similar, in the sense of being very useful, but not very truthful. It's like a magical power which we assign to a coherent group of particles which we observe to exist as a unified body. In theory, the massive object consists of a group of parts. But the theoretical parts, in summation, of each one's "mass" cannot account for the quantity of power that the unified whole is observed to have as "mass". So to be truthful we should represent this power which is attributed to "mass", as something which is produced by magic, or magically comes into existence, when parts are unified as a whole.

If time is unreal what are colors and sounds, these phenomena being defined in terms of time (Hertz)? :chin:

In a Timeless Universe, how are colors and tones defined?