Constant velocity is motion in a straight line at a constant speed. --------------------------------------->Skip to Relative Velocity

Objects at constant speed travel the same distance every second.

Velocity = distance/time

v = d/t

The object below has traveled to the right 20 cm in 10 seconds. It moves forward 2 cm per (for every) second.


You notice that it does not travel more or less than 2 cm during any one interval. Because we know how it is currently moving, and if we assume that it continues to move this way (if there are no unbalanced forces) we can use some simple relationships to predict certain situations in the future.


In the example above, the object travels 20 centimeters in 10 seconds. By applying some simple logic, we know that it travels forward a distance of 2 centimeters per second (velocity) or 1 cm every 0.5 seconds. If every centimeter of travel takes 0.5 seconds, we can assume that it would take 50 seconds to go 100 cm.

So to find the time it takes an object (at constant v) to go a given distance can be predicted using

t = distance/velocity

t = d/v

In the same way, we can use logic to figure out some way of determining how far objects go in a certain amount of time. In the example above, we watched an object move forward 20 centimeters in 10 seconds. If we accept that nothing changes, it would go 40 centimeters in 20 seconds or 2 centimeters for every second.

We can predict distance using

distance = velocity x time

d = vt

So now we can predict how a marble or tank or airplane or skateboard or planet or ant or baseball or bird or photon or soccer ball or tau neutrino will travel when there are no unbalanced forces acting on them.

Go to Relative Velocity