Principles of Technology

Project: The Bridge



It is your task to design and construct a free-standing structure ("bridge") which will be capable of supporting a minimum of 5 gallons of water. There will be 2 divisions:

Standard Division - materials are limited to hobby sticks and white glue as supplied by the school

Open Division - any student-supplied materials are allowed, as long as they are appropriate and fall within normal safety parameters. No individual piece of rigid material can be longer than 15 centimeters (6 inches).


Rules and Regulations for the Competition:

1. Your bridge must be constructed by you, and made from pieces of suitable material no greater than 15 centimeters (6 inches) in length.

2. Your bridge will be weighed prior to the beginning of the testing phase.

3. Your bridge must span 18 inches and be free-standing. This means no permanently mounted supports of any kind, including (but not limited to) the following: nails, screws, reinforced concrete, or any thermonuclear fasteners.

4. Your bridge should be designed to support a minimum of 5 gallons of water for 30 seconds before collapse. The water will be poured into a 5 gallon plastic bucket suspended from the center of the span.

5. Your bridge will need some sort of hook to hang the bucket from (see #4 above). This hook is considered part of the bridge and needs to be installed onto your structure before the weigh-in.

6. In the (unlikely) event that your design fails to support the full 5 gallons of water, you will need to be able to calculate the actual weight of water that your wimpy structure was able to hold. Some handy conversions:

1 ft^3 of water = 62.4 pounds

1 gallon = 0.134 ft^3

7. Your final results need to be expressed as a ratio of the weight of the bridge to the weight of water held.

8. Each student is required to turn in their own bridge and write-up - no group efforts.

9. Refer to the Bridge Project Cover Sheet for a detailed summary of how you will be graded for this project.



The Bridge Project Cover Sheet

This is how your Bridge will be graded (100 points total)

Be sure to staple this sheet to the front of your write-up before you turn it in.


Journal and Design Plan : 20 points

A detailed plan for your bridge, with appropriate dimensions

A journal detailing your efforts

A list of materials needed for construction

Step by step process for the construction of your bridge

Construction : 30 points

Does your bridge look like your plans?

Does your bridge look like it was thrown together or thought through?

Operation : 10 points

Does your bridge stand and support its own weight?

Will it support any additional weight?

Calculations : 10 points

Total mass of your bridge _______________ grams

Total mass of water held before failure ________________ grams

Ratio: Mass of water to the Mass of Bridge ( mW / mB )

Final Project Write-up : 30 points

What does a ratio greater than 1.0 indicate? What if it is less than 1.0?

What did you like about your design? Why?

What didn't you like about your design? Why?

What would you do differently next time so your bridge would hold more weight?

What did you learn from this project?


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