1. My Science book gives the vaguest explanation of "varying velocity". To understand it better I've then divided it into various concepts. However so to know better could you please explain the correct words in Physics for these concepts. I will show you the concepts I gave.

First there is a change in that speed changes but not the direction.

Then there is change in that direction changes but not the speed.

Then there is both change in direction and speed.

All these things in my book are termed varying velocity. I would be very grateful if you might give the correct terms for each of these varying velocities or perhaps then it is I have got it completely wrong and some or all that is are not part of the concept varying velocity.

2.

3. I think what's difficult is understanding speed vs. velocity. A velocity is a speed in a given direction. You have to name the direction. That's why changing direction or speed is equally a change in "velocity". So, it's not just another fancy word for "speed". It's a different thing from speed.

http://en.wikipedia.org/wiki/Velocity

We can talk about two objects with opposed velocities (moving in opposite directions), but we can't talk about two objects having opposed speeds, because there's no such thing as negative speed.

4. Even though there's no such thing as opposed speeds. Speed can change and I think that's the issue. As long as you acknowledge that I don't understand how no change in direction but a change in speed is not varying velocity. However if you take into account acceleration I think this becomes easier to understand as we have a term that describes what's going on there. Still I would think that it would better if there was a term to denote change in direction and speed. I hope there is one anyway?

5. Originally Posted by LotusTiger
My Science book gives the vaguest explanation of "varying velocity". To understand it better I've then divided it into various concepts. However so to know better could you please explain the correct words in Physics for these concepts. I will show you the concepts I gave.

First there is a change in that speed changes but not the direction.

Then there is change in that direction changes but not the speed.

Then there is both change in direction and speed.

All these things in my book are termed varying velocity. I would be very grateful if you might give the correct terms for each of these varying velocities or perhaps then it is I have got it completely wrong and some or all that is are not part of the concept varying velocity.
Velocity is a vector. A vector has two aspects, a magnitude and a direction. Change either and you change the vector.

The magnitude of velocity is speed.

So to vary velocity you can vary the direction, the magnitude (speed) or both.

6. So a Vector is like duel-combination whereby one of the duel possibilities if changed changes the vector in so the vector is defined as a "totality" of possibilities direction and speed and not one of these things "specifically" in the "sense" that one be it speed or "rather only" direction were saying here determines a "specific" vector as one kind of vector over another.
So it's not that the change of speed that determines change in Vector as that it is only Speed that does this or "can" do this (or rather with the same thought that direction does this and only that direction can do this). This would be the false thinking here. So what you’re saying is as a combination of speed and direction a change in one of it's sub-possibilities be it speed or direction changes the vector as one into another.

So I'd call it a "combination sub-possibility openingdetermination" if that's alright. Opening meaning that it' is the change in one that opens the possibility that it becomes a new vector but that change in both can make it a new vector. It's just the change in one "opens" up the possibility it's a new vector.

7. you're making something very simple difficult.

Its a vector quantity. A speeed with an associated direction. To change velocity you need to change speed or direction, and, either involves an acceleration ( also a vector quantity, as opposed to change in speed ).

8. If you are driving a car and you accelerate your speed, you will feel yourself being pressed against the seat back, or if you step on the brake you will feel yourself pitch forward. This is acceleration due to a change in speed. If you go around a bend without changing speed, you will feel yourself pitching sideways. This is acceleration due to a change in direction. Maybe this will help you see why the two kinds of acceleration are sort of the same.

9. Originally Posted by LotusTiger
So a Vector is like duel-combination whereby one of the duel possibilities if changed changes the vector in so the vector is defined as a "totality" of possibilities direction and speed and not one of these things "specifically" in the "sense" that one be it speed or "rather only" direction were saying here determines a "specific" vector as one kind of vector over another.
So it's not that the change of speed that determines change in Vector as that it is only Speed that does this or "can" do this (or rather with the same thought that direction does this and only that direction can do this). This would be the false thinking here. So what you’re saying is as a combination of speed and direction a change in one of it's sub-possibilities be it speed or direction changes the vector as one into another.

So I'd call it a "combination sub-possibility openingdetermination" if that's alright. Opening meaning that it' is the change in one that opens the possibility that it becomes a new vector but that change in both can make it a new vector. It's just the change in one "opens" up the possibility it's a new vector.
Take a look at an introductory, say high school level, physics text. There should be a chapter or so on vectors. It is sometimes also found in a junior-senior high school algebra book. You will find it discussed geometrically (arrows) and algebraically (ordered pairs and triples). You will need to get that under your belt to understand what we are talking about. It is pretty easy once you get the basic idea (and clear as mud until you actually go through it in print).

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