Introduction

People have always sought to stretch the bounds of the human experience to the heavens. This fascination has been evident in many ancient civilizations; in Greek mythology, for example, a man named Daedalus flew with wax wings. In 1783, this dream was realized by the brothers Montgolfier, Joseph Michel and Jacques Etienne, when they conducted an unmanned balloon flight. The early focus of the development of flight was on balloons and its later sibling, the dirigible (Croteau & Worcester 233); however, theoretical flying machines have been proposed ever since the time of Leonardo da Vinci. He came up with the idea of a helicopter, something like an airplane, and a parachute (Wolters 152). His idea of a parachute was not the first one, however; the earliest known sketches date back to 1480 (Wolters 153).

In the history of the development of the parachute, there have been several significant events. The first-known successful attempt at a parachute jump came in 1797 with the inventor André-Jacques Garnerin (Wolters 153). After that, parachuting was little more than entertainment; not until WWI did parachuting became a serious endeavor. Parachutes gave aviators a safety net to fall back on when they were shot down (Stuttman 1830). During WWII parachutes created a new kind of soldier—the paratrooper. Flown in by transport planes, the paratroopers would plummet thousands of feet down into enemy territory. This allowed the soldiers to infiltrate the enemy lines without engaging in land combat.

The parachutes used during WWII have since evolved to allow greater control and accuracy, but the basic design remains the same. The parachute’s primary components are as follows: the pilot parachute, main parachute or canopy, suspension lines, harness, pack, and ripcord. The pilot parachute is released when the ripcord is pulled and guides the main canopy out of the pack. The suspension lines connect the canopy to the harness which is attached to the parachuter (Stuttman 1834). The size and shape of the parachute varies with its intended function, but the canopy usually is either circular or rectangular and its diameter ranges from 7 m(for humans) to 30 m(for heavy-equipment) (Encarta).

After the parachute opens, the canopy creates friction with the air because of its rapid rate of descent. At first, the friction is greater than gravity and thus slows the parachute’s velocity. But as the velocity decreases, the friction decreases as well. When force of friction equals the force of gravity, there is no overall force acting on the parachute and so it descends at a constant rate (Macauly 115). This rate is known as the terminal velocity. It occurs when the maximum velocity is achieved and the air resistance equals the force of gravity (Giancoli 30).

The goal of this experiment is to find out how the weight of the parachuter affects its terminal velocity. Since terminal velocity occurs where the forces, including gravity, on it are equalized, increasing the mass of the object will increase the gravitational pull, thereby altering the terminal velocity. We hypothesize that the parachuting figures’ weight is directly proportional to the terminal velocity.

Procedure

In order to test our hypothesis, we decided to drop the parachuting action figures from the top of a flight of stairs. Before collecting data, we tested various ways of controlling the descent of the paratroopers. First, we tried stringing one fishing line through the top of the parachute to guide its fall, but the line had a tendency to become tangled in the paratrooper’s suspension lines. This tangling prevented the paratrooper from reaching its terminal velocity by not allowing the parachute to fully open. Next, we tried stringing two lines through the sides of the parachute, but we found this greatly reduced the rate of descent through friction. We finally settled upon simply allowing it to free fall. While this method did allow the paratrooper to collide with obstructions such as the wall and the flowers at Sarah’s house, it seemed to be the most accurate way to collect data.

Once we had settled upon a method for data collection, we decided that we need to conduct trials with twenty different weights. For each of the weight levels, we conducted three trials in order to increase accuracy. We increased the weight by tying a length of fishing line onto the paratrooper and then attaching fishing weights. Proceeding to take down the times for various trials, we decided that neither of us wanted to run up and down the stairs sixty times. We got around this problem by creating a kind of elevator with fishing line and tape. The procedure which we settled upon was for Jeremy to drop the paratrooper and for Sarah to time its descent, after which she would attach our little elevator to the top of the paratrooper, he would pull it up, and the cycle would begin anew. We would coordinate the drop and the time by counting "1, 2, 3, drop!" and releasing and timing the paratrooper at the same time.

The data which we collected came in the form of times from the sixty trials and from the varying weights that were used for the trials. We were able to calculate the terminal velocity by using the formula @ X/t since the paratrooper hit terminal velocity almost instantly. We found the average time for each weight and we measured the distance from the floor to the top of the stairs to be 4.07 meters. The following table displays the data that we collected.

 

Data File: data1.txt
Using this data, we attempted to model the relationship between weight and terminal velocity. Here is a graph that shows how our data relates.

Conclusion

The weight v. terminal velocity graph shows that the relation between the weight of the paratrooper and its terminal velocity is roughly linear. Thus, our hypothesis would seem to be accurate. However, the small size of our sample prevents us from observing the end behavior of the function. Thus, it cannot be determined whether the function is linear of exponential.

As with any experiment, there are many sources of error. The small height from which the paratrooper was dropped may have contributed to the inaccuracy of the experiment. A higher dropping point would enable us to have more accurate data, allowing for differences in the time due to environmental changes. Though we tried to take uncertainty into account by taking three trials of every weight and averaging the time, more trials would have created a more accurate time average. The reaction time of the timer and the dropper may have also played a role in creating error.

There are many ways that we could improve the experiment. First, improvement could be made to the environment. Though the experiment was conducted indoors where air currents were minimal, a windless chamber would have been better. Other improvement include: a higher dropping point, more trials for each weight, a larger number of weights, and usage of another paratrooper.

Through this research project, we learned a lot about the scientific method. Jeremy was surprised at how much time it would take just to get a working setup done. Sarah learned how interesting experimental science could be as well as what it was like to have a verbose perfectionist as a research partner. Jeremy got some good lessons on how to insult people, while Sarah had fun giving the lessons. Sarah perfected her disgusted expression through Jeremy’s insistence on actually working on the project. Jeremy, as always, was constantly hungry and managed to bum some Oreos and Ritz crackers off Sarah. On the whole, we feel this research project was a very beneficial learning experience.

Bibliography

Croteau, Maureen and Wayne Worcester. The Essential Researcher. New York: HarperPerennial, 1993.

Giancoli, Douglas C. Physics. Englewood Cliffs, New Jersey: Prentice Hall, 1991.

Macualay, David. The Way Things Work. Boston: Houghton Mifflin Company, 1988.

"Parachute." The New How It Works. Westport, Connecticut: H.S. Stuttman, Inc. Publishers, 1989.

"Parachuting." Microsoft Encarta Encyclopedia. 1996 ed.

Wolters, Richard A. The World of Silent Flight. New York: McGraw-Hill Book Company, 1979.
 

Related Links

Parachutes  A skydiving publication

Paratrooper Cartoons of the 50s-60s Era

Tandem Parachuting  Description and brief history of tandem parachuting

The Flying ELVI  Parachuting Elvis impersonators

Flightnet Skydiving Links

Wild Geese Skydiving Links
 
 

Back to Top