Surface Area’s Effect to Air Drag

The objective of this experiment is to investigate the answer of the following question: “How do the surface area of a rotating propeller of a helicopter affect the average velocity of its free fall when it is released from a constant 4m height?” Velocity of the helicopters are affected by air drag. Air drag doesn’t have a stable formula. As the speed of the objects that are exposed to air resistance changes, components that affect the magnitude of air drag force changes. For example, for low speeds the air resistance is directly proportional to the velocity, but for high speeds the air resistance is directly proportional to the square of the velocity. Since I didn’t know if the velocity of the helicopter models will be high or low at the beginning of the experiment, I controlled elements that affect the air friction in both high and low speeds. A helicopter model was used to measure the effect of cross-sectional area on the velocity. I tried to make the model’s features as similar as possible to a real helicopter. There were 2 propellers and there were masses under the propellers. The surface area of the propellers of the helicopter model were decreased by decreasing the length and width of the propellers proportionally and models were released from the certain height, 4m. The landing times were recorded. The height was divided by the times needed for landing and the average velocity was found. The graph of area vs velocity was sketched. The effect of surface area on air friction and eventually velocity was found by interpreting the graph. The graph showed that the cross-sectional area of the propellers is inversely proportional to velocity. From this it can be understood that the models are in the category of the low speed vehicles