When is a physical quantity a vector?

Hi! Great question. A vector has 2 bits of information within it and can be summarized by using an arrow with a particular length. The length of the arrow represents the magnitude of the vector. The direction of the arrow represents the direction of the vector. Doing math with vectors is very useful because you can do vector math with them. For example, you can move the vectors wherever you want but you cannot change their direction and magnitude – only where the vector starts. You can put vectors end to end such that the head of a vector touches the tail of another vector to add them. For example, if you are traveling in a boat north east at 30 mph but the wind is pushing you at 30 mph south east then you are actually travelling due east. You can see that when you draw the vectors end to end. The resulting direction and magnitude starts and ends at the tail of the first vector and the head of the 2nd vector. Great question and hope this helps.