
Re: Negative value of Velocity?
Billy Wight Dec 28, 2011 4:43 AM (in response to Legt Chevrollier)Velocity is a vector quantity, and therefore can be negative (i.e. flow direction is opposite the coordinate axis positive). Velocity resultant can not be negative, but individual components of velocity can be. Are you looking at a resultant, or component of velocity? And to be picky, pressure can only be negative relative to a reference point, for example gauge pressure vs. absolute pressure. Hope this helps.

Re: Negative value of Velocity?
David Maxham Jan 2, 2012 9:15 AM (in response to Legt Chevrollier)I think you're mixing up the terms velocity and speed. Velocity, as Billy indicates above, is a vector quantity and therefore can be negative or positive. Speed is a scalar quantity and because of the way it's defined, is always greater than or equal to zero, since speed is defined as the magnitude of the velocity, that is, the square root of the sum of the squares of each velocity component in a Cartesian coordinate system.

Re: Negative value of Velocity?
Legt Chevrollier Mar 5, 2012 6:01 PM (in response to David Maxham)Thank you for the replies, both of you.
Now I understand it:
velocity is a vector quantity, and speed a scalar one.
