Changes

:<math>v(t)={\mathrm{d}x \over \mathrm{d}t}</math>

:<math>v(t)={\mathrm{d}x \over \mathrm{d}t}</math>

where ''x'' is the position and ''v'' is the velocity. The velocity is a [[vector]], and its length or absolute value is called the ''[[speed]]''. The velocity has dimensions of length / time, and may thus be expressed in meters per seconds (in scientific usage).

where ''x'' is the position and ''v'' is the velocity. The velocity is a [[vector]], and its length or absolute value is called the ''[[speed]]''. The velocity has dimensions of length / time, and may thus be expressed in meters per seconds (in scientific usage), or miles per hour in more common usage.

For an object moving along a straight trajectory, if [[acceleration]] and velocity have the same sign, the object is gaining [[speed]].  If acceleration and velocity have different signs, the object is losing speed.

For an object moving along a straight trajectory, if [[acceleration]] and velocity have the same sign, the object is gaining [[speed]].  If acceleration and velocity have different signs, the object is losing speed.