the formula: R = (.5)DpAv^2 is used to determine how much air resistance (resistive force) is being placed on the object. R is the Resistive force. D is some dimensionless empirical quantity called the drag coefficient p is the density of air A is the cross-sectional area of the object (surface area) v is velocity My question is, is the density of air some constant that should be already given to me? also, how would i go about finding the drag coefficient? I'm asking this because in physics we're doing a lab in wich we drop a cofee filter... and we record its time to reach a certain height (which im guessing is to be able to calulate for the terminal velocity). So in other words, I have all of these variables except for R, D, and p. Can anyone help me out?