Physics Learning Center

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Cancelling in Equations - Learning cancelling in an equation. What is a cancelling in here meant? You simplify and remove a pair of numbers or symbols in an equation that is called cancelling. That's a significant difference when using a cancelling instead the ordinary way without cancelling. You could finish an equation quicker and easier but make sure that you don't make un-proper cancelling and then your answer get wrong.

Here are some common examples of cancelling in physics, you might explore the others and make a lot of practices during handling your equations.

The Mechanichal Energy Conservation
Sometimes you don't see the mass of a body in alot of mechanichal energy conservation questions. That's no problem completely,you still have posibilities to solve the problems with unknown mass. Take a look the mechanical energy equation below for instance

What is the better next step for that? Of course cancelling all "m" on the both sides of the equation, even for an equation with a mass value given because the all "m" must be the same in values. Than we get the simpler equation as below.

The next step, inserting your data!

The Momentum Conservation Equation
Some momentum problems involve two bodies with the same in masses.

For the different masses just insert your data, usually then it can be cancelled as below for instance

Some Improper Cancellings
Make sure you don't do things like these!

If you insist to remove the 1/2 from the equation, do this step

Below the bernoulli equation, some students do wrong cancelling in this equation

if you want to remove the ρ on ρgh and 1/2 ρv2, should be like this:

Even some students do thing like this!!!

So be carefull in cancellings, practices make you better, do alot!

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