# Air Resitance for Trajectory

1. Apr 3, 2005

### mabramovich

Hi:

I'm to write a program ("game") in which two tanks take shots at each other, with a user who inputs firing angle, gravitational acceleration and the like, I'm sure you've all heard of it.

Anyway, I'm having trouble in dealing with air resistance. Without knowing too much on the subject (not covered in any particular detail at the grade 11 level) the equation for drag is of course:

$$F_{D} = \frac{1}{2}C\rho\\Av^2$$

The problem I have is for calculating velocity for use in that formula. First of all, I would I assume I would take both the x-component and y-component of velocity and vector-add them to get a composite velocity, but the formulae normally given for a velocity at time, $$t$$, ignore air resistance, for example:

$$V_{y} = sin\theta\\-gt$$

There is of course no problem if a constant air resistance, $$F_{air}$$, is used, but air resistance is directly proportional to velocity, so I'm in a bit of a loop here, do I not have a problem of requiring velocity to calculate air resistance and air resistance to calculate velocity?

Any help is greatly appreciated, and of course not just a formula but an explanation.

Thank-you.

2. Apr 3, 2005