Vectors are different from scalar numbers because they also include information about direction. Velocity, acceleration, force, and displacement are all vectors. Speed, time, and mass are all scalar quantities. Acceleration can be either a scalar or a vector, although in physics it’s usually considered a vector. For example, a car traveling at 45 mph is a speed, whereas a car traveling 45 mph NW is a vector. When you draw a vector, it’s an arrow that has a head and a tail, where the head points in the direction the force is pulling or the object is moving.

The coordinate system you use can be a compass (north, south, east and west) which is good for problems involving maps and geography, rectangular coordinates (x and y axes) which is good for most problems with objects traveling in two directions, or polar coordinates (radius and angle) which is good for objects that spin or rotate.

We have to get really good at vectors and modeling real world problems down on paper with them, because that’s how we’ll break things down to solve for our answers. If you’re already comfortable with vectors, feel free to skip ahead to the next lesson. If you find you need to brush up or practice a little more, this section is for you.

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The next four videos are a review of what we’ve covered so far with vectors. If you jumped here without going through the first two sections on 1-D Kinematics or Newton’s Laws, watch these four videos now to get an overview of vector components, resultants, trigonometry, resolution, and component addition. If you’ve already worked through these, then skip down to the section on relative velocity and start there.

Here’s a basic introduction to scalars and vectors:

Click here to go to next lesson on Resultants.

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