Wednesday, April 15, 2015

terminology - Why and how does negative velocity exist?


Why and how does negative velocity exist? I have read on the internet about negative velocity but I still don't understand how it can even exist since time is positive and so is length. By doing some math I came to the conclusion it can't and should not exist and yet there are so many papers and videos trying to explain it.



Answer





  • Velocity is a vector. Speed is its magnitude.

  • Position is a vector. Length (or distance) is its magnitude.


A vector points in a direction in space. A negative vector (or more precisely "the negative of a vector") simply points the opposite way.


If I drive from home to work (defining my positive direction), then my velocity is positive if I go to work, but negative when I go home from work. It is all about direction seen from how I defined my positive axis.


Consider an example where I end up further back than where I started. I must have had negative net velocity to end up going backwards (I end at a negative position). But only because backwards and forwards are clearly defined as the negative and positive directions, respectively, before I start.


So, does negative velocity exist? Well, since it is just a matter of words that describe the event, then yes. Negative velocity just means velocity in the opposite direction than what would be positive.


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