Scalars vs Vectors Scalars – a quantity that only needs a magnitude (with a unit) to describe it Ex: Vectors – a quantity that needs a magnitude (with a unit) and a direction to completely describe it and there are many others still to come… So vectors are generic tools, developed specifically for Physics, used to help us solve physics problems and explain things more clearly. You’ve never heard of them before because Bio & Chem only deal with scalar quantities, so your teachers never needed to mentioned there were also these things called vectors.

We use arrows to represent a vector quantity in a diagram its length represents the magnitude of the vector, according to the units set by some scale Choose a scale so that your diagram will be as large as possible in the space provided, but no arrow will need to be longer than your c-thru. the arrow tip indicates its direction according to some directional key Try one: Draw the velocity v = 30 km/hr, East What should we use as a scale?

So finally, v = 30 km/hr, east would look like: scale 1 cm = 2 km/hr & key N W + E S Note: the tip should be drawn very carefully so to not change the length of the carefully drawn arrow. Now let’s look in the text at some more examples on page 29.

Vector Components Consider the following: for a displacement of something that ends up SW of where it started, that could have come about by that object moving so far directly W, then so far directly S… The legs of the right triangle are the components of the original vector

OR, for a plane that flies with a velocity in the NW direction, that could be because the plane’s engines where moving it W while the wind was blowing it N… Again, the legs of the right triangle are the components of the original vector

they are vectors themselves they lie on the main directional axes Sometimes in Physics (actually, quite often!) it is important to know the value of the components of a vector there are 2 for each vector they are vectors themselves they lie on the main directional axes they’re perpendicular to each other if added together, their sum equals the original vector The process of determining the components of a given vector is called resolution, or, another way, to resolve the vector into its components. Let’s try one….