1. The problem statement, all variables and given/known data I made a wind tunnel for a science project and i am trying to determine its windspeed. I decided to suspend a pingpong ball on a string in the wind tunnel and measure the angle change. But to do this i need to calculate the drag force and i cannot do this without knowing the drag coefficient of the ball. 2. Relevant equations Drag force: 1/2*P*v2*A*Cd x=vit + 1/2*at2 3. The attempt at a solution One idea i have is to drop the same ball from a height and measure the time it takes to hit the ground. I then use the equation x=vit + 1/2*at2 and solve for a. Then, using 1/2*P*v2*A*Cd = ma, i solve for Cd, and use this drag coefficient to solve for wind velocity in the wind tunnel. However, i think i cant simply put ma= drag force becuase this suggests that gravity equals drag force which would mean the ball was at terminal velocity. How would you solve this?