What about air resistance
What about air resistance? Next time you are in your car, put your hand out the window. You can feel the air pushing against your hand. Hopefully, you will notice the following:
The faster the car moves, the greater the force the air pushes on your hand.
If you make your hand have a bigger surface area (like going from a fist to flat hand), the air resistance increases.
The air resistance also depends on the shape of your hand. OK, you probably wouldn’t notice this, but it’s true.
Putting this all together, we can use the following model for the magnitude of the air resistance force.