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Technology, Science & Alt Science / Re: Is there such a speed slower than no speed at all?
« on: February 22, 2007, 04:59:26 AM »For the component of the velocity in the direction you have resolved.Quote from: Robin SThe magnitude of a velocity is always positive by definition, but when you resolve in a particular direction (for example, the direction opposite to the direction of travel) you may obtain a negative value.
a negative value for what?
Say that we define a fixed cartesian co-ordinate system for our velocity to be measured relative to (since all velocities must be measured relative to something). Then, taking the units of metres per second resolved parallel to the x, y and z axes, it is entirely possible that we will obtain three negative values. In other words, starting at the origin and allowed to travel for 1 second, our object might end up at the position (-3,-2,-5). The magnitude of its velocity would still be positive (in this case, sqrt38 metres per second) but we have resolved it in directions which give negative components. There is no contradiction at all here, since we are measuring two different aspects of the velocity: its magnitude, and its components parallel to fixed axes.