Doing a physics experiment where we are required to calculate the acceleration from gravity, for a simple high school assignment. And as part of an extended discussion, I would like to take into account air resistance aswell. But looking into the formula, I notice that there are a lot of variables included in it. Such as drag coefficient, rho, velocity, and area.
Which are the best values to assume for these variables if I want to get an average value for the effect of air resistance on gravity?
Context: Dropping a 1.5cm diameter marble from a ceiling onto floor, in a room of about 20 degrees Celcius. And the main aim is to calculate the gravity of earth using the constant acceleration formula. All I need this air resistance value for is to manipulate the equation of acceleration to get it closer to the value of 10m/s^2, constant of gravity. Formula I'm talking about: Cd * .5 * rho * V^2 * A
Also what does the velocity part in the formula mean? The initial velocity, the final velocity of the marble?