Talk:Speed

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[edit] speed

Speed is the essence of things. Such a common expression.

It all started with my having to help my daughter write an article on "Slow down, you are moving too fast". I have read a book by an American Author called James Gleick - not sure if I got the name correct. He wrote a book called Speed. He is also the author of a book called "Chaos". I am looking for this book. Wonder if anyone can let me know the correct name of the author.

How comes speed and acceleration have no direction _ They are vectors and definitely they have directions.

If you want to know anything about motin or otherwise just speak to a West Bromwich Fan


Speed isn't a vector, it's scalar. Velocity is a vector (speed+direction). And acceleration has direction only indirectly.. you can accelerate by either speeding up (forwards) or slowing down (backwards), though which direction you are moving doesn't matter, you're either slowing up or you're slowing down. And who on Earth is West Bromwich... >_< Dan 00:08, 14 January 2006 (UTC)

[edit] list of common speed

I think it is useful to have a list of speed for common moving objects. Please join me if you agree. --Leo 14:59, 20 April 2006 (UTC)

Yep... Speed is scalar... So Velocity is more accurate to use... No one runs backwards as fast as they run forwards... So it mus tbe treated accordingly

[edit] Average Jogging Speed or World Class Marathoner?

A world class time for a marathon is less than 2.5 hours. That translates into about 16.8 km/hr or 10.5 miles /hr. While it would be wonderful if we all jogged at 10 miles / hr and could dream of hitting record paces if we trained a few extra hours everyday, these atheletes are slightly out of the league of the "average long distance jogger".

I agree. As an avid runner myself who enjoys running 10k or so every other day, I never get those kinds of speeds. I have a GPS watch which tells me my speed, and If im feeling good, I can keep up 13km/h for 30 minutes. Then I come here and read the average speed is 16kph for long distance. Theres no way that can be accurate. I can see it being possible for the professional marathon runners, but I myself, am already considered above average I think. I would say an average run speed, based on my observations of other people, is around 9km per hour.007craft 16:31, 14 June 2006 (UTC)

I would say 5-6 mi/h or about 8-10 km/h could be considered reasonably "average" for a long distance runner. For a concrete example, the median finishing time for the last New York marathon was about 4:39, which corresponds to a speed of 5.6 mi/h. Itub 16:11, 19 June 2006 (UTC)

[edit] Question

I'm sorry if this isn't the place, but has a page for "instantaneous speed" been created? Or is there a page from which I can aquire information on it? If not that might be a nice addition to this page as well.

het where is the speed and the egg color and the Icubation


                    help kendra

[edit] 4 times energy for doubled speed

I have a question,

Why when you double the velocity of an object, you quadruple its speed rather than doubling it?

Has it anything to do with E=mc2 wherein mass is converted into energy by the square of light?

I mean if you "put" kinetic energy into an object, will part of it become "potential mass" and the rest actually become kinetic energy? Is that what explains why you have to square the number of times you want to increment the velocity in order to know the energy/power required?

I've looked everywhere and no one seems to explain why you have to square the energy in order to increment the velocity


I think you are a bit confused. When you double the velocity, you do double the speed in the direction traveled. All speed is, is the magnitude of the velocity. Therefore both forward 3 m/s and backwards 3 m/s have the velocities +3 m/s and -3 m/s, respectively. They have the same speed, 3. What gets quadrupled is the kinetic energy. KE = (1/2)mv^2 where m is mass and v is velocity. If we plug in 2v for v (i.e. doubling velocity), we get the new kinetic energy (1/2)m(2v)^2 = (1/2)(m)(2^2)v^2 = 2mv^2. We see this is quadrupled since 4*(1/2)mv^2 = 2mv^2. As for the other part of the question about the role of E=mc^2. This equation comes from special relativity and tells us how much energy an object would have if all mass could be converted to energy. This formula is only useful with other energy equations when an object is moving at a substantial fraction (at least 10%) the speed of light and thus is not relevant to everyday calculations of velocity, speed, momentum, or energy.Aohara1986 06:42, 19 October 2007 (UTC)

[edit] Notation

The article should use a consistent notation for speed; actually it´s difficult to read because of different symbols and the use of |v|. I think it could use v for velocity and v (in normal text) for speed, which is common notation for vectors and scalars. --Canaima 01:14, 19 October 2007 (UTC)