Calculating the Drag Coefficient of a Parachute for a Dragster

by Evan Hunt

Submitted : Fall 2009

For this project I have been asked to find the coefficient of drag created by a parachute, used to slow a dragster down after crossing the finish line. As well as the stopping time and max g-force caused by the chute. I was given several key measurements to use in my calculations, the dragsters speed when crossing the finish line was given (120 m/s), along with the distance to stop using only brakes (600 m) and the distance to stop using both brakes and a parachute (200 m). First I began by solving for the time it took the dragster to stop when using only brakes. Once I found this, I was able to find the deceleration caused by the brakes. Using the (in order to remove time from the equation). Now knowing both the drag coefficient and the constant, I again used the velocity function to solve for time at velocity final (0). To find the max g-force I used the acceleration equation, inputting 120 m/s for the velocity because the most acceleration would be at the highest speed. Taking this value I divided it by 9.8 m/s2 giving me the max g-force the driver of this car would experience. From this project I found the coefficient of drag to be .3377, the time using brakes and parachute to come to a complete stop from 120 m/s to be 4.37 s, and the max g-force to be 5.36 g's.equation for acceleration which was modified to incorporate the force of the parachute, I then took the derivative and second derivative giving me both the velocity and position functions relative to time. Manipulating the velocity function to equal time, I plugged it into the position function. This gave me a position function with only one unknown, the drag coefficient. After solving to get a value for the drag coefficient by setting the position function equal to 200 m, I then used this new value to solve the velocity function for the unknown constant at time equal to zero.

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