2. A few key equations

It's useful to know a few key equations, so you can link causes and consequences. It's rare to be able to explain 100% of all phenomena, but experience will show you that knowing how to explain 95 or 98% of a phenomenon by known variations in parameters is often considered very efficient. In any case, it generally avoids starting from a position of major impossibility.

Example 1: These fluids, whose viscosity increases when you try to move them fast, include certain plastics with a high concentration of mineral fillers.