1^st Quarter Project Guide

The professor will divide the class into groups of 3 to 4 students each. Each group will be supplied the following items to aid in construction (quantities are at left in parentheses):

1. (4) 6-inch lengths of 1/2-inch PVC pipe
2. (6) 6-inch lengths of 1/2-inch PVC pipe, with one hole drilled through the center
3. (4) 9-inch lengths of 1/2-inch PVC pipe
4. (1) 24-inch length of 1/2-inch PVC pipe, with holes drilled 6 and 7.5 inches from one end, and 0.5 inches from the other
5. (8) 90-degree 1/2-inch PVC slip elbows (20 g each)
6. (2) 1/2-inch PVC slip x thread elbows (29 g each)
7. (6) 1/2-inch PVC Tees (26 g each)
8. (1) 1 1/4-inch x 1/2-inch PVC Tee (82 g)
9. (1) 8-inch 3/16-inch diameter welding rod (28 g)
10. (2) 42-inch shoe strings (7 g)
11. (1) 4-inch by 7-inch rectangle of cloth, with eyelets near each corner (6 g)
12. (4) wooden wheels with axles (23 g each)
13. duct tape
14. various masses
15. a meter stick (approx. 153 g for wooden, 220 g for plastic, 297 for 2 m stick)
16. a balance

The 1/2-inch PVC comes in two thicknesses; the thin pipe has a mass of about 4 g per inch, while the thick has a mass of about 6 g per inch. The approximate masses of the remaining items is given in parentheses at the end of each item.

One rubber "ramp" is available; it has a mass of 197.5 g.

The project rules are:

1. You do not have to use all of the materials if your design does not require them, and you may petition the instructor for additional materials, but petitions are not guaranteed to be granted.
2. None of the materials may be altered in any way. All must stay in the lab.
3. Your final design must be approved, constructed and tested no later than the beginning of the fifth laboratory class meeting.

   Note that you will be required to address an inherent stability problem before your final design is approved.

   After design freeze, photos of the final designs will be available here.
4. Range measurements are to be made relative to the axis of the throwing arm, to the point of first contact with the floor.
5. All range data must be averages of multiple measurements, with error bars.

   You may make as many trial throws as you want, but your average range and absolute error must be based on a minimum of 10 throws.

   All measurements entering into your average and error calculations must be reported.
6. All performance evaluation deliverables are due at the beginning of the last class meeting.

Your performance evaluation must include the following deliverables:

1. A scale drawing of the final design, and a list of the materials used.

   This Mathematica notebook might help for this item and the next.

2. Calculation of the 3-dimensional distance the center of mass moves during the standard throw of juggling cube, 20 inch sling and 1 kg counterweight.
3. A graph of the experimental range of the trebuchet as a function of the mass of the payload, and a theoretical calculation of same.
   • Counterweight mass must be 1 kg, and sling length must be 20 inches.

   This Mathematica notebook might help for the theoretical calculations on this and the remaining items.

4. A graph of the experimental range of the trebuchet as a function of the mass of the counterweight, and a theoretical calculation of same.
   • Payload must be a juggling cube, and sling length must be 20 inches.
   • Counterweights to test are 1 kg, 1.4 kg, 2 kg and 2.4 kg.
5. A graph of the experimental range of the trebuchet as a function of the effective length of the throwing arm, and a theoretical calculation of same.
   • Payload must be a juggling cube, and counterweight mass must be 1 kg.
   • Sling lengths to test are 10, 15 and 20 inches.

©2010, Kenneth R. Koehler. All Rights Reserved. This document may be freely reproduced provided that this copyright notice is included.

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