Trebuchet Essay

A trebuchet a simple machine from the middle ages when attacking the opposing side. The Chinese invented the trebuchet in 300BC, the French were using trebuchet more than anyone.

A force is a push or pull, but if unbalanced it can change an objects motion. The force used in a trebuchet is gravitational force, which is applied when the counterweight is pulled to the ground to launch the projectile in the air. The counterweight has to be heavier than the projectile or the trebuchet won’t work. The force that is applied is a non-contact force as the two objects (Counterweight [agent] and gravity [Receiver]) don’t touch but if it was a contact force then the two objects would be touching. Some examples are

A trebuchet is a first class lever as

the order goes load, fulcrum then effort. Second class levers go effort, load then fulcrum and a third class lever goes fulcrum, effort then load. The Effort is applying pressure to move the load to a higher level and the fulcrum is a point where it can turn or be balanced. Some diagrams of types of levers would help. Mechanical advantage is a factor by which a force is magnified. This calculated by load moved  effort applied. What does mechanical advantage have to do with your assignment?
The experiment was performed by launching the projectile from the trebuchet, adding an extra 50g after 4 trials. This was repeated until the counter-weight mass reached 150g. The task sheet stated the purpose of the experiment was to, design and evaluate the use of a trebuchet as a simple machine and determine the relationship between the counter-weight mass and the projectile distance.

The variables in this experiment was the dependent variable, the distance. The independent variable, was the counter-weight. Finally, the controlled variable was the length of the throwing arm.

Variables Table
Dependent
Variable Independent Variable Controlled
Variables
The thing that was being measured was the distance. The thing that was changing each time was the counterweight The things that stayed the same was where it was measured from and the length of the throwing arm.

Hypothesis:

It was hypothesized that if the counter-weights mass increases then, the projectiles distance will increase.

Diagram:

Equipment:
 1 x roll of electrical tape
 9 x hexagonal pencils
 1 x round base pencil
 1 x 30cm ruler
 1 x small plastic medicine cup
 1 x bouncy ball (projectile)
 Scissors
 Tape measure

Method:
STEP 1: After all materials were collected they were put together to build a trebuchet as seen in the diagram above.

STEP 2: Once trebuchet is built, the class headed outside to a bigger area to test the trebuchets.

STEP 3: All trebuchets are lined up with a tape measure along the ground to see how far the projectile goes.

STEP 4: Launch the projectile 4 times with a counterweight of 50g.

STEP 5: Write down all results in m then calculate the average.

STEP 6: Add another 50g to the counter weight so it’ll be 100g.

STEP 7: Launch another 4 times writing down all results and calculating the average at the end.

STEP 8: Add an extra 50g to the counter weight so it’ll be 150g.

STEP 9: Launch the projectile another 4 times writing down all the results and calculating the average at the end.

STEP 10: With the results, take the averages and the counterweights mass and turn it into a scatter plot.

Risk Assessment:
Risk Injury Prevention Solution
Equipment being damaged Broken window, not being able to use the tennis courts. Go outside in a big area and be cautious when using the tennis courts. Tell classroom teacher if a window is broken. Go to a different area.
Sunburn / over heated Red, burning hot skin. Dehydration. Wear a hat, put on sunscreen or go to a shaded area. Get a drink of water. Move to the shade to cool down and if burnt put on sunscreen.
Falling over Arms or/and legs hurt with bruises or grazers. Watch where you’re walking, don’t run. Tell the Teacher, tell the student its okay.

Results:

Mass (g) Trial 1 (m) Trial 2 (m) Trial 3 (m) Trial 4 (m) Average (m)
50 (g) 0.07 0.09 0.18 0.12 0.15
100 (g) 0.32 0.27 0.25 0.33 0.29
150 (g) 0.3 0.41 0.43 0.46 0.4

Analysis & Discussion:

Graph 1 shows the mass of the weights and the average distances with different masses.

Each different mass (50g, 100g and 150g) was trialled 4 times each and then an average was calculated. The experiment performed supported the hypothesis made which was that if the counterweights mass increases than the distance travelled by the projectile would increase. Why is it supported? Explain using data. The trebuchet worked by holding back the throwing arm and then letting the throwing arm go. Once let go, gravity acts on the counterweights as its heavier (non-contact force) and the projectile was launched where did you get this from? More weight causes the arm to move faster, which is what causes the projectile to launch further.. As the counterweight got heavier the distance increased because gravity acted

quicker.

Evaluation & Recommendations:

If the experiment was performed again, then a change that can made would be to change to length of the throwing arm from 11cm to 13cm so then it could get that extra distance.

It would achieve extra distance as the throwing arm is taller so the projectile will get time in the air. The problems with the final design for the trebuchet was that, the group couldn’t change the length to the desired length of the throwing arm. This was because the frame wasn’t tall enough. If the experiment was to be repeated with a baseball being launched then, some modifications that would be made would be; to make the trebuchet bigger, make the frame taller so adjustments can be made to the throwing arm so the desired length can

fit.

Conclusion:
Overall, the hypothesis supported the experiment. The hypothesis was that if the counter-weights mass increases then, the projectiles distance will increase. Also levers are very important as they help with everyday lives. Levers have many uses like helping us to dig (shovel), walk (legs), open bottles (bottle opener) and carry big loads of dirt (wheelbarrow).

Acknowledgements:
I’d like to acknowledge the people in my group Annabel, Stephanie and Madison. Also I’d like to acknowledge Mr Brunello for helping me throughout this assessment.