# First law of thermodynamics

When thinking about thermodynamics, we will first thing about “matter is not destroyed just transformed etc.…”

When there is no change of energy in our system, then :

Now, a simple example:

We have a fan that uses 25 watts of energy, so, let’s say I want to know how fast is the wind that the fan blows(speed of the wind from the fan), so basically

Applying thermodynamics first law:

There is no change in the wind of energy in the system so:

Which remains:

Now, that just means that the energy (watts) is going to be transformed into kinetic energy (wind´s speed), so:

Notice that this is the typical $Ke=1/2mv^2$ , which can be express in a rate form too by getting the mass to be a mass unit per time, now for the velocity we have

Note: thermodynamics is also understanding, remembering and comprehending units.