Somewhat similarly to friction, air resistance also acts as a retarding force.

The real world is not the same as idealized beginning physics situations; for example, projectiles will not follow the path of a parabola, unless they are in a vacuum.

Also, this air resistance is not a constant value, but instead it is proportional to velocity.

In situations with air resistance the acceleration is not constant either, to deal with that you can express acceleration as dv/dt (the instantaneous acceleration).

Since derivatives are involved, the use of integration, and methods such as u-substitution, can be used to solve these more complicated motion problems.

Because integrals can be complicated, computers were invented for greater artillery accuracy in wartime.