What is a Vector?

Physicists use two different kinds of quantities, scalar quantities and vector quantities. Scalar quantities, like mass, volume, and speed, have one component -- whatever it is that you're measuring.

Vector quantities include a scalar component, called magnitude, and also a directional component. Velocity, for example, is speed in a certain direction. Other common vectors are force and acceleration.

A Vector is graphically shown by an arrow which has a length showing its magnitude and a direction.

In the image to the left, the red arrow indicates the force pushing the rocket up. Forces always include a directional component, which in this case points straight up. The length of the arrow indicates how strong the force is: the longer the arrow, the greater the force.