Physics, Block 2
Mr. Elwer
Trebuchet Project
I. Introduction
1. Background Info
- Trebuchet uses potential energy of counterobject to throw an object.
- The potential energy of counterobject will become the kinetic energy of a throwing object.
- The team who will earn the highest efficiency will win provided that other elements like weight of counter object is same.
2. Purpose
- Students were to throw an egg using a trebucheet of their own.
- The egg was to hit the point that was 25m away from the trebuchet. (Accuracy)
- Students could feel the real world physics with real world experiment.
3. Hypothesis
- As the size of the trebuchet is limited, the one who can pull the most amount of potential
energy, torc power, and least amount of energy loss will win.
II. Materials
- Enough wood board
- Two wood stick (throwing arm)
- Basic design (We used FAT(Flying Arm Trebuchet), but changed into the classic one)
- Cutting & assembling devices ( Zigsaw, saw, screws, a drill, etc )
- a strong string (sling)
- a bag to put an egg in.
- screwable metal thing that is curved to form a hole
- long metal stick
III. Experiment Design
1. Prepare the place to work on. Buy all needed supplies, or collect left-overs that can be used as
materials.
2. Sketch the design on the wood board.
3. Cut the wood
4. Assemble the wood using screws. (Pre-screwing is essential)
5. After the assembly of body, prepare to make the slinger with the bag and string.
6. Make two holes in the opposite site of the bag.
7. Tie a string firmly on the holes.
8. Make a trigger by putting two metal things on the board and putting a metal stick through them.
9. Make throwing arm by connecting two long wood sticks.
10. Put a nail with about 45 degrees at the end of the throwing arm. It is to put the slinger and let it
go smoothly in the right direction.
11. Test, and fix accordingly.
IV. Variables
1. When competitng with other teams, the place and time should be same as different wind and
geographicl features results in a totally different data. (Control)
2. The counterweight should be less than 50 pounds. (Independent Variable)
3. The size of a trebuchet has to be less than 1m^3 (Control)
V. Design
1. Our trebuchet had 1m x 1m x 1m size.
2. Its design was classic (thus, no reference page was needed in this project).
The only difference was that its sling wasnt connected to the throwing arm.
3. The slinger was made up of a string and a plastic bag.
4. Other design is described at III.
VI. Data Table
| Launch 1 | Launch 2 | Launch 3 |
| ∆x=16. 2 m | ∆x= 11.4 m | ∆x=13.6 m |
| Height of Angle = 42 degrees | Height of Angle= 38 | Height of Angle= 43 |
| Mass of an Egg = 60g | Mass of Counter Weight = 13.6 kg | Launch time = 2.6 s |
| | Launch 1 | Launch 2 | Launch 3 |
| Max Height | 3.6m | 6.4 m | 3.7 m |
| Launch Vy | 9.1 m/s | 11 m/s | 9.2 m/s |
| Launch Vx | 6.2 m/s | 4.4 m/s | 5.2 m/s |
| Launch angle & Velocity | 55 degrees 11 m/s | 68 degrees 12 m/s | 61 degrees 11 m/s |
| Average Acceleration of Trebuchet | 12 m/s2 | 13 m/s2 | 12 m/s2 |
| Force and Impulse of Trebuchet | .74 N .63 Ns | .80 N .66 Ns | .70 N .72 Ns |
| Mechanical Advantage and Efficency | 1 (due to inaccurate numbers and less sig. fig.) | 1.16 (simply wrong. Due to inaccurate measurement- probably at the launch time) | .84 (acceptable(?)) |
VIII. Conclusion
The launch angle was significant element that could be overlooked. Inaccurate models had capricious angle values; thus, the distance was varying as well. In other words, besides the body, the slinger was important factor in the efficiency of a trebuchet.
