(1) General rules for vectors

Some physical properties, such as temperature or area, are given completely by their magnitude and so only need a number (called a scalar ) to represent them. But there are other physical quantities, such as force, velocity or acceleration, for which we must know direction as well as size or magnitude in order to work with them. It is often very helpful to represent such quantities by directed lines called vectors . Because vectors carry the physical information of both magnitude and direction, using them gives us a very neat way of handling these quantities.
The drawing below illustrates 3 rules for working with vectors.
some demonstration vectors