# Separation of variables tutorial

__Key concepts:__**Differential equations**
**Separation of variables**
**Speed and distance**
Question 1:
"*A car of mass, m, is moving at a speed v0 is put in neutral and gradually gets slowed down by an air resistance force that is some number times the speed of the car. Determine its speed as a function of time.*"
To figure out this question, we need:

A sketch of the situation we are trying to describe

A differential equation that tells us how the change in speed depends on time and other variables

A strategy for solving this equation

A way of checking that the result makes sense