Embedded Files
Evidence of work
Evidence of work
My group — Joey, Olivia, Alisa, and I — had to build a trebuchet. The trebuchet had to have a base, legs holding up an axle, and, of course, an arm to launch a clay projectile. Our objective was to launch our projectile the greatest horizontal distance we could. Our parameters were that the contraption could not have any parts exceeding a length of one meter in any direction at any given time during the launch. It also had to be reusable and able to launch a projectile on its own.
After securing the legs to our base — having already measured the distance between them, of course — we found a metal pipe under one meter long and drilled a hole through the center so we could place a bolt through it, and secure said bolt to the legs. This allowed the arm [metal pipe] to rotate a full 360° and have a full range of motion. Lastly, we attached a cup to one end of the arm, and attached a screw to our base that we could wrap the rubber bands — pulling the arm back — around.
We did this twice. The first time, our trebuchet capped out at about 15 meters, averaging 10. When we got to remake our trebuchet, we did the same things we did when making the first, but were more precise; the new model could launch clay projectiles over twice as far.
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*This graph is based on information taken from the original trebuchet design which we used to improve the second design. All calculations were found with information from the original design as well.
Spring Potential Energy: potential energy stored in the structure of an object that occurs when [temporary] elastic deformation is applied to it through work; e.g. compress, stretch, etc. In this case, the spring potential energy of our trebuchet was stored in the stretch of our rubber bands. The equation is PE = ½*k*x² where k is the spring constant and x is the distance the rubber bands are stretched. The spring potential energy of our trebuchet was 10.72J.
Gravitational Potential Energy: the potential energy an object possesses right before colliding with the surface of the Earth. The equation is PE = m*g*h, where m is the mass of the object, g is the acceleration due to gravity — 9.8m/s² — and h is the height of the object. We calculated this for our projectile; a clay ball with a mass of 10g and a height of 5cm. The result was about 0.0049J.
Kinetic Energy: the amount of potential energy converted. The equation is KE = ½*m*v², where m is the mass of the projectile and v is the total velocity of the projectile. The result was 1.81J. (Note: compare this to spring potential energy, not gravitational potential energy)
Horizontal Distance: the change in position of the projectile from its starting point — the cup on the trebuchet arm — to where it lands.
Efficiency: percentage of potential energy converted to kinetic energy. The equation is %Efficiency = PE/KE. The result was 17% efficiency.
Vertical Velocity: the speed, at which, the projectile traveled vertically. The equation is Vv = Ag*t, where Ag is acceleration due to gravity and t is time. The result was 4.51m/s.
Horizontal Velocity: the speed, at which, the projectile traveled horizontally. The equation is Vh = d/t, where d is distance and t is time. The result was 18.5m/s.
Total Velocity: the speed the projectile traveled — with horizontal and vertical aspects combined. The total velocity is the hypotenuse of a right triangle, in which, the legs are the vertical and horizontal aspects of velocity. The equation is Vv² + Vh² = Vtotal² or Vtotal = √(Vv² + Vh²). The result was 19m/s. (Note: √ is the radical symbol)
Spring Constant: the constant factor of stretch (or compression) of a spring. The spring constant equation is k = F/d. The result was 49N/m per rubber band, for a total of 343N/m for our seven rubber bands. (Note: spring constant is part of Hooke´s Law)
Reflection
Reflection
During this project, I communicated and collaborated well. I communicated well by sharing my thoughts and ideas regularly — making sure to contribute to the project, as well as by listening to the thoughts and ideas of my fellow group members. I collaborated well by sharing the work load evenly, while also trying my best to keep my team mates on task. I learned that I work almost just as well with people I don´t know as I do with those whom I do know.
In the future, I can improve my critical-thinking and citizenship skills; during this project, I feel like I did not attempt to solve problems as practically as I could have. I also feel like I did not act as tactfully as I could have; since I did not know half of my group members, I had a difficult time communicating with them in a diplomatic fashion. I hope to improve on these skills by thinking more practically and behaving in a more ethically-appropriate manner.
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