photo credit: quapan

Physics equations are filled with symbols that each represent a specific value or type of value.

I remember when I was taking physics in high school and I was SO frustrated with all of the symbols!  How are you supposed to remember what they all mean?  Why does it have to be so complicated?!?

The truth is, all the symbols were chosen eons ago in an attempt to make physics LESS complicated.

You see, symbols are not necessarily set in stone.  There is absolutely no reason why you couldn’t make up your own system of symbols for everything and use those instead … and, to add to that, there is no reason why your physics instructor couldn’t make up his or her own system too.

In no way is it wrong to say … change the velocity equation from:

v = x/t, where

  • v = velocity
  • x = distance
  • t = time

to

:) = :( / :D , where

  • :) = velocity
  • :( = distance
  • :D = time.

These two equations are exactly the same equation BUT (and this is a big but) can you imagine what would happen if your teacher used the second version and then you changes schools (or classes) and the new teacher had a whole different set of symbols!  You’d be screwed!

This is why the symbols have been standardized over the years …. there are still a few variations out there … but generally most textbooks and instructors use the same set of symbols.

  • V = velocity
  • t = time
  • g = acceleration due to gravity
  • a = acceleration
  • x = horizontal distance
  • y = vertical distance
  • ….. and so on

What’s with all the “little” symbols?

In addition to the regular symbols like shown above physics also has sub-symbols which again, seem to make life confusing, but are really there to make it less confusing…. you’ve seen them … the look like:

V1, V2, Vo, Vf or

F1, F2, Fx, Fy

What the heck are those for?

The little symbols or sub-symbols are just descriptions that help to make the bigger symbol unique.

This is best explained with a NON-Physics example:

Let’s say you had three pairs of shoes and for some insane reason you wanted to describe them with a symbol instead of with words.  So, you invent a symbol for the word “shoes”

Ø = shoes

But your shoes are NOT all the same.  Each pair is different and so you need to add a description to your symbol so that you can tell them apart.  Immediately you think of describing them by colors so you decide to use that as a sub-symbol description like this:

Øblack Øred Øbrown

But then you find that writing all those descriptive letters down is tedious and takes too long so you decide to shorten the words like this:

Øb Ør Øbr

Now instead of having to write “black shoes” you only need to write Øb.  It’s quick, short and handy.

This is all that sub-symbols are in physics!  They are  just a quick, easy way to describe something so you don’t get it confused with other things.

You can add sub-symbols to an symbol to help keep things organized.  The whole point of them is to make it simpler for you to remember what means what … and, if you can’t remember, CHANGE IT!

For example… if your given a problem and they give you three velocities: V1, V2 and V3 but you find that those extra numbers tucked into your equations are confusing go ahead and give them NEW sub-symbols that are less confusing!

V1 = Va

V2 = Vb

V3 = Vc

Simple.  Done.  No confusing numbers.

Just make sure you write down in your problem that you are changing the symbology.

That being said…

There are a few sub-symbols that you really shouldn’t mess with because not only are these symbols descriptive, they are also crucial hints to solving the problem at hand.  Here are a list of the ones you should leave alone:

  • x (like Fx, Vx)
    • x means horizontal so when you see a sub-symbol that’s an x it means that the value is in the horizontal direction (like Fx means “force in the horizontal direction)
  • y (like Fy, or Vy)
    • y means vertical …. so just like above, when you see a sub-symbol y it means that the value is in the vertical direction.
  • 0 (like V0)
    • 0 is a common one in physics that tends to mean “initial” or “at the beginning” …. so V0 would be the initial velocity.
  • f (like Vf)
    • f in physics typically means “final” or “at the end” so Vf would mean final velocity.