An introduction to Physics

What is Physics? Where is it situated in general scheme of the sciences?

We can define Physics as the study of the basic nature of matter and the interactions that govern its behaviour. Physics is a discipline that investigates nature's principle to discover how they work. Physics tries to describe these principle with no ambiguity using the most precise and compact language we have : the language of  Mathematics.
From this point of view we can consider Physics as the most fundamental of the sciences: when we talk about Biology, Chemistry, Geology, etc. we can say that Physics underlies all of them.
For example modern Chemistry uses Physics (in particular the subfield of Quantum Mechanics) to explain how atoms combine to form molecules .
Anyway a single statement about Physics is incomplete, and it's quite hard to give a an exhaustive definition of Physics that satisfy everyone. The easiest way to give a sense to what Physics is and does, is by listing some of its subfield and exploring their content.

The list below shows an exemplification of  the major subfields of Physics.

 Units of measurement and  their conversion in the Metric System

Physics uses quantitative models to test its hypothesis. These models lead to predictions that can be tested by making measurements.
To make measurements we will use the METRIC SYSTEM because it simplifies the units of measurements conversion a lot. As a matter of fact the Metric System is based on standard prefixes to represent multilples of ten:

For example a kilo-meter is equal to 1000 meters or meters, a mega-byte is equal to 1.000.000 of bytes or, in a more compact way, bytes.

The units of measurements, meters, bytes, kilograms, etc. are connected to the particular property or quantity we want to measure. Different units of measurements systems actually exist; during our course  we will use only one of them: the so-called "SI", International System for Units of Measurement.
In the SI only five fundamental units of measurements exist:

every other quantity different from distance, time, mass, current or temperature can be expressed from these. For example in the SI  we measure

velocity by using:
accelaration by using:
force by using:

and so on.