PHYSICS 103

Parachuting in Sewanee

Use the material provided up to the limits indicated:

Plastic foil wrap (up to 1 m long per team), 13-gallon trash bag

Straws (up to 20 per team)

Wood dowels (up to 3 per team), 3/16” in diameter, 36’ long.

Stapler, Duct tape, Scotch tape, String

Must use: Plastic Cup, 9 oz size (one per team), mass of about 10 grams

Must use: Tennis Ball (one per team), mass of about 56 grams

Objective: to design an apparatus that, when dropped from the roof, will have the maximum time in the air. The time to land t_f must be less than 10 seconds (getting stuck on a tree or wall would disqualify it!). Score will be calculated as:

Score = t_f *50 if t_f <=10 seconds (for example a time to land of 2 seconds will give you 100 points).

Score = 0 if t_f > 10 seconds

There will be a deduction of 10 points from the score if the apparatus does not make it to the ground intact, and a deduction of 10 points if it misses the landing circle.

Considerations:

An object in free fall will reach a constant terminal velocity v_t,when the downward directed force of gravity is equal to the upward directed drag force.

v_t =[ 2mg / dAC_d ] ^1/2

where m = mass

g = gravitational acceleration

d = density of air

A = cross sectional area

C_d = drag coefficient

The competition will be held next Friday  (September 2) launching from the Observatory roof top . We will conclude the event having lunch together.

Brainstorming

Select one person as recorder, and one as moderator.

The recorder will keep track off all of the ideas suggested. S/he will record on a board during the class time, but save a record of the notes for your report.

The moderator will keep things flowing and attempt to enforce the rules.

RULES

Get everybody's name and email address.

Try not to pass judgment ideas during the brainstorming session itself. Do not point out why something will not work, or is not as good as another idea. All ideas are potentially good so do not judge them until after the session. Avoid discussing ideas at this stage, which includes not criticizing and not complimenting ideas.

Write down all of the ideas. At this point of the process, there are no bad ideas. The more ideas there are at the end of a session, the greater the probability of one of them being a really good idea, or leading to one.

Try to build and expand on the ideas of others to see where it might take you. Let other people's ideas be an inspiration for your own.

Explore the parameters of the known equations.

Encourage everybody to participate. Every person has a valid viewpoint and a unique perspective on the situation and solution. In a brainstorming session you can always put forward ideas purely to spark off other people and not just as a final solution.

Each idea presented belongs to the group, not to the person stating it. You are not in competition with each other. It is the group's responsibility and an indication of its ability to brainstorm if all participants feel able to contribute freely and confidently.

Construction

You will be given time on Wednesday to construct a model that incorporates your design goals. Usually the process would involve constructing a prototype model, testing that, and then producing improved models, and repeating as necessary.In the interest of saving time we will skip these steps.

Report (due a week after, one per team)

This exercise has a simple report.

1. Must include a list of everybody in the group.

2. Include a description of the brainstorming session including the ideas recorded at that time.

3. Describe how you chose your final design.

4. Describe your construction process. You should include a drawing of your apparatus.

5. Include your final drop time and overall score.

6. Indicate how you would improve your design based on the experience gained.