In our trebuchet, we made a base, two legs on the side, which the axle/fulcrum goes into, and an arm to actually launch a projectile, which swings around the legs. On the arm, we have a nail sticking out of the back of it, with a string tied around it, and a clay projectile attached to it. On our base, we have three sets of two rubber bands looped around the base, and these rubber bands attach to another nail on the opposite side of the first nail on the arm. The rubber bands create enough force to launch the projectile.
Modifications
1st modification: We first had a small cup attached to the arm, but it didn’t make the projectile launch very far. So instead, we cut an 8 inch string, which the projectile attaches to, and the string was tied to the nail which was attached to the arm. This made the projectile launch a bit farther.
2nd modification: We used rubber bands instead of weights, because it makes the projectile go farther.
3rd modification: At first, we didn’t have a stopper, but other groups had them and they seemed to work well, so we were gonna use a stopper as a modification. We added a stopper and launched the projectile, but it didn’t work. We tried to fix and improve it, but it still didn’t work very well and worked better without the stopper, so we decided to get rid of the stopper.
4th modification: In the beginning, we only had two sets of three rubber bands. There was barely any force applied of this, and the projectile barely went anywhere. We added another set, but with only two rubber bands, and we took one off of the other two. Now, we had three sets of two rubber bands, which was attached to a nail on the base, and to another nail on the arm.
5th modification: The rubber bands never stayed on the nail that was attached to the base, So we got rid of the nail, and just looped the rubber bands around the base so it would stay on. But now, the rubber bands were too short so we couldn’t pull back the arm enough to launch, So we added one rubber band to each set. Now, we have three sets of three rubber bands.
6th modification: The projectile wasn’t able to launch very well because the arms were to loose and wobbly, So, we added pieces of wood which were also attached to the base, in front of the arms in order to create arm stability, which helped to make our projectile launch farther.
7th modification: Another one of our modifications was base stability. The rubber bands wrapped around the base were twisted, making the base lift up a bit and it wasn’t very stable. We straightened the rubber bands to keep the base more stable.
8th modification: We started out with thin rubber bands, which didn’t create force to launch the projectile very far. So, we changed our rubber bands to thicker ones, which had more force, and made the projectile launch farther.
Mass of projectile- 22.5 grams
Horizontal distance- 2.5 meters
Time in air- 1.45 seconds
Vertical Distance- (d=½ a t^2) - d=2.6 meters
Horizontal Velocity- (v=d/t) - v=1.72 m/s
Vertical Velocity- (v=at) - v=14.21 m/s
Total Velocity- (a^2 + b^2 = c^2) - 3.117 m/s
Angle of Release-
Spring Constant- (k=F/d) - 88.2 Joules
Initial Spring Potential Energy- (PEspring = 1.2 k v^2) - PEspring = 428.46 Joules
Kinetic Energy of the Ball- (KE = ½ m v^2) - KE = 109.3 Joules
Percent Energy Converted- (KE/PE) - 25%
6. Our trebuchet is stable and consistent.
Alternative Energy Car
For our hybrid car, we had to design and make a vehicle that could transport two rolls of fifty pennies five meters. My group and I took a different approach to this project than other groups. We bought mini skateboards, called tech decks, and we were originally going to roll two skateboards taped together down a ramp with the pennies attached to them. That didn't work very well, so instead we changed our idea to a slingshot. We had three sets of three rubber bands attached to two nails that were thirty centimeters apart. So, we put the attached tech decks in the middle of the rubber bands, pulled back and let go. At first, the tech decks would only go one to three meters, but we made modifications to it, and we were able to make them go past five meters.
Reflection
I can say I did well on this project, but I could've done better. I came up with some ideas for the trebuchet and hybrid that helped to make it better, although I could've thought of more. When I try a bit harder, I do a good job, and I have a good and positive attitude when it comes to facing a problem or obstacle.
I feel I have a lot of empathy toward my team members, and I like to be organized and keep my notes neat. I could have more leadership while working with a team, and also time management. For the future, I'm going to show a lot more leadership and work ethic.
Concepts
Distance vs. Time - Distance vs. time is simply the change in distance compared to the change in time. You can also use this to find velocity.
Velocity - Velocity is the change in distance over the change in time. The equation for velocity is distance divided by time (v=d/t). It is measured in meters per second (m/s). Velocity is used whenever an object moves.
Potential Energy - There are two types of potential energy. These are both measured in Joules (J). They use PE as a variable. Gravitational - Gravitational potential energy is the energy an object has due to its height. The equation for gravitational PE is PE=mgh, where m is the mass, g is the acceleration due to gravity (9.8m/s), and h is the height from the object to the ground. Anytime an object is above the ground it has potential energy.
Spring - Spring potential energy is the energy stored from an object deforming, like a spring stretching. Spring PE is PE=1/2kx^2, where k is the spring constant, and x is the displacement of the spring stretching. Anytime a spring is stretched it has spring potential energy.
Kinetic Energy - Kinetic energy (KE) is the energy an object has due to motion. The equation for KE is KE=1/2mv^2, where v is velocity, and m is mass. It is measured in Joules, Any time an object moves it has kinetic energy.
Thermal Energy - Thermal energy (TE) is the energy lost due to heat. It is found by adding the PE and KE, then subtracting that number from the total energy. Anytime an object has heat it also has thermal energy.
Friction - Friction is the result of molecules rubbing together in opposite directions. Anytime two surfaces rub against one another, they have friction.
Spring Constant - Spring constant is the energy required to compress a spring. The unit used for the spring constant is k. The equation for the spring constant is k=F/x, where F is the force applied to the spring, and x is the distance the spring stretches. Anytime a spring is stretched, it has a spring constant.