Average Speed vs. Average velocity

[Checkfate]

If you are so 'aware' of the difference between vector and scalar quantities, then you should be more careful when writing equalities.

By the way, wth is this? Can you point out my error rather than just saying there is a mistake and I am not aware of the difference between scalar and vector quantities? Thanks.

 

[caprija]

2v :P

caprija, about your question :) "What is the instantaneous velocity between 0 and 3 seconds?"

It sounds like the question is asking you for the average velocity between 0-3s. So your approach is right, you would take two points that lie on the on the line of best fit between x=0 and x=3 and then calculate the slope of that line. :) If you want to show your teacher that you understand it is a velocity (vector) then put \vec{v}=+0.7km/min :)

Is the portion of the graph between 0-3s a straight line?

Thank you so muchhhhhhhh :)

You helped a lot :)

Thanks :)

 

[radou]

By the way, wth is this? Can you point out my error rather than just saying there is a mistake and I am not aware of the difference between scalar and vector quantities? Thanks.

Cool down, no one is insulting you. I just wanted to point out that you can't write (which you did in one of your previous posts, and if it was a mistype, then I apologize) something like \vec{v} = 0.7 [units] because it does not make any sense. However, you can write, for example, \vec{v}=0.7\vec{i} [units].

 

[Checkfate]

caprija, wait.. I was wrong. Since your graph is a distance vs time graph it is impossible to find velocity, read one page back. Sorry mate, I was in a rush and didn't really think it through. According to the data you have supplied, it is impossible to find the velocity. What course is this for? If you have not learned about vectors, maybe they just misused the word velocity and meant speed. To be safe I would put v=0.7m/min.
Unless you have a displacement time graph, then you could find velocity. :) But at least now you know the difference between velocity and speed, tell your teacher tommorow that you aren't able to find velocity because you don't know the displacement :P (displacement is the distance and direction by the way, whereas distance does not specify direction, you will learn about it soon.)

 

[Checkfate]

Radou, okay sorry, I did feel insulted as it felt like you were saying that I did not know what I was talking about while I feel strongly that I know the difference between a vector/scalar quantity. But eplain to me why you need the vector symbol on the units? In my physics class \vec{v}=0.7m/min would meen 0.7m/min in a positive direction (The + is assumed). We don't put a vector sumbol over 0.7m/min. If I am doing something wrong within this paragraph please tell me :) I can't say that I am failing physics though... and I think I would be if I didn't have a grasp on how to use vector quantities by this point! lol :) Why do you have \vec{i} in there?

 

[radou]

"Direction" and "orientation" mean the same thing in this context.

Hm, in my language, by mentioning 'direction', we refer to the straight line on which the vector is 'placed'. My fault, direct translation. But, how do you call that 'direction' then? (Assuming we know what magnitude means, and assuming when you say, for example, 'direction north', you mean that the 'arrow' is pointed north.)

 

[radou]

...In my physics class \vec{v}=0.7m/min would meen 0.7m/min in a positive direction (The + is assumed). We don't put a vector sumbol over 0.7m/min. If I am doing something wrong within this paragraph please tell me :) I can't say that I am failing physics though... and I think I would be if I didn't have a grasp on how to use vector quantities by this point! lol :) Why do you have \vec{i} in there?

Have you learned about vectors in math yet?

 

[Checkfate]

No, just physics. I have wanted to peak at vector calculus for a while now, but haven't yet.

 

[radou]

No, just physics. I have wanted to peak at vector calculus for a while now, but haven't yet.

I suggest you do so, it will become more clear.

 

[jtbell]

Hm, in my language, by mentioning 'direction', we refer to the straight line on which the vector is 'placed'. My fault, direct translation. But, how do you call that 'direction' then? (Assuming we know what magnitude means, and assuming when you say, for example, 'direction north', you mean that the 'arrow' is pointed north.)

I see your point. We can say that a line's orientation is horizontal, and its direction is either to the left or to the right. I think in practice, in English, "direction" almost always includes both things. People often do use "orientation" to mean what you do, but it's also used as a synonym for "direction" so it can be confusing unless the context is clear. I can't think of a word that people would reliably recognize as meaning your "direction," without a very clear context to put it in.

And with vectors specifically, the description "magnitude and direction" is universal in physics textbooks in the U.S., as far as I know.

 

[Checkfate]

radou I am sorry to say this but I think you are misinterpreting my point... We are dealing with a physics problem, and in physics, \vec{v}=0.7m/s is the correct way of writing that the velocity of something is 0.7m/s in a positive direction. I would beg to differ that I need to read a vector calculus book (university material) to understand vector notation which is clearly and simply laid out in grade 10 physics courses. While in vector calculus, one set of rules may be used, but as far as I know they don' teach vector calculus in grade 10 so I don't think that someone should have to understand a university level concept to grasp a grade 10 level concept...caprija's is in grade 10 after all. If you want to carry out this discussion further, perhaps we should move it to private discussion. I am not saying that you are not right as you obviously have a few years on me :P But in a physics courses in the United States and Canada, my definitions as well as my examples hold true. (except the one that I admitted was miscalculated) "Case Closed"

 

[radou]

I see your point. We can say that a line's orientation is horizontal, and its direction is either to the left or to the right. I think in practice, in English, "direction" almost always includes both things. People often do use "orientation" to mean what you do, but it's also used as a synonym for "direction" so it can be confusing unless the context is clear. I can't think of a word that people would reliably recognize as meaning your "direction," without a very clear context to put it in.

And with vectors specifically, the description "magnitude and direction" is universal in physics textbooks in the U.S., as far as I know.

I think I got it. A vector is completely described with magnitude and direction if we set up a coordinate system, because a point with the coordinate (x, y, z) is enough to determine the radius-vector from the origin, with the 'arrow' on the top, i.e. in the point (x, y, z). Further on, for every point (x, y, z), we can define the vector of an 'opposite orientation' with it's 'top' at the point (-x, -y, -z). Pointing out that the vector is described with three parameters, obviously makes sense only if we haven't got a coordinate system set up.