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Speed and velocity

Reading Ian Stewart's book ¨17 Equations that changed the World¨ I came across the following statement on page 38:
` ¨To understand Galileo's pattern we need two everyday concepts (! bold and underlined are mine) from mechanics: velocity and acceleration. Velocity is how fast something is moving, and in which direction. If we ignore the direction, we get the body's speed. Acceleration is a change in velocity, which usually involves a change in speed (an exception arises when the speed remains the same, but the direction changes).¨`
The way I interpret this, velocity is a vector and speed is the corresponding scalar. In everyday life, whatever physicists and mathematicians like Mr. Stewart say, I reckon both concepts are used as synonyms, but in this special physical case the difference is important. It reminds me both of what happens with many words in German (see Fremdwort, although in the present case both speed and velocity are of Latin origin) and even more so of what happens in Spanish with the concepts of dirección and sentido, where the first indicates the route between two points, the second if the route is taken from one point A to the other point B or the other way around. So in Spanish a dirección has two sentidos. It is not the same to go from Villarriba to Villabajo or from Villabajo to Villarriba. German could cope with this saying something like auf der Strecke zwische Villarriba and Villabajo hat sich in Richtung Villabajo ein Unfall ereignet. Der Trampelpfad wird in beide Richtungen vorläufig für den Bergziegenverkehr gesperrt. And then, when a language like English allows for it, you can also take the change in speed or in velocity into account, which other languages like German or Spanish do not allow so easily. But it seems to me it would be good if they could, it would make the description more accurate and precise. But how could this be accomplished?

There was a picture of a comic I have here, I have erased it because Lawyers behave like assholes sometimes and I do not want to give them excuses to fleece me. Imagine Fat Freddy, if you know what I mean...

Kommentare

Am 12.03.2014 um 11:08 von Christian
I never thought about the difference velocity speed. Good to know it now.
Im alltäglichen Sprachgebrauch wird ein Körper auf einer Kreisbahn die Geschwindigkeit beibehalten, aber durch die Querbeschleunigung die "Geschwindigkeit im Raum" ändern. (So z.B. der Mond um die Erde, wenn wir mal eine Kreisbahn annehmen.)
Noch etwas: ein Vektor hat (in meiner Erinnerung) sowohl Richtung als auch Orientierung (und zusätzlich eine skalare Größe); eine Strecke ist ein Skalar.
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