Velocity indicates the speed of an object in a direction of motion. For example, if you say a car is going 30 mph, you are talking about its speed. But if you say it is going 30 mph in a north direction, you are talking about its velocity. We distinguish between speed and velocity because if you add the speeds of objects, their directions are important. For example, the velocity of an airplane with respect to the ground would vary according to the direction of the wind.
Vectors help determine total velocity Adding velocities at angles can be difficult.
Thus, scientists use a graphical method called vectors to help calculate the sum of velocities in a given direction. The way this works is that you draw a picture with lines or arrows representing different velocities. Combining the speed with the direction of the arrow, you get its velocity. This can be a very handy tool in such a calculation. Acceleration Acceleration is the increase of velocity over a period of time.