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Negative velocity


What does it mean when you have negative speed or velocity?


Strictly speaking speed is just a number, it is velocity that could be positive or negative.
Velocity is a vector which means it has direction as well as size.

A negative velocity just means that you are traveling in the opposite direction.

For example:
An ant crawling across this page from left to right might have a velocity of + 0.1 m/s
If it crawled from right to left at the same speed its velocity would be 0.1 m/s.

This idea is pretty important. Imagine the different result of a car at a set of traffic lights moving off at - 2 m/s (lets say - represents backwards) rather than at + 2 m/s (forwards).

© Keith Gibbs 2013