FIRE AWAY
The goal of this project was to design a trebuchet that could launch a clay ball as many meters possible. The trebuchet must have a base, two legs that hold up an axle, and a lever arm. The device must be easily portable and have no dimension larger than 1 meter. We were constantly changing things throughout the building process. Once we found a variable that was altered to the most efficiency we moved on the the next, trying to constantly improve on the design and functionality to create our final product.
The original model had to have an arm, an axle, counterweight, projectile holder, string trigger, hook, and a sturdy base. After some research and experimentation we made some changes. The angle of the nail holding the rubber bands was first, we put the nail in at a 110 degree angle for the most efficiency. The lower angle, the further the ball will fly. At 110 degrees the ball flew 5.95 meters. After that, we altered nail that held the load to the side of the board for more force. Next, we changed was the axle holding the arm in place, the old one we used broke under the pressure of too many rubber bands so we found a new bar. The new bar that we get was one solid piece of wood instead of many, so there was less friction when the arm spinned around. Last, we also changed from weights to rubber bands for creating the force that would project the clay ball. After taking some measurements we discovered that using weights and rubber bands should have the same results since they are both equal to 10N. Theoretically there should have been no difference between the two, but there was. One issue was size. The weights were large and cumbersome while the rubber bands we slim. We were able to get more rubber bands on the arm that weights, creating more force.
We had to find all the calculations of the ball like distance horizontal, time in air, velocity horizontal, velocity vertical, velocity total, release angle of projectile, spring constant, spring potential energy, kinetic energy of the projectile, and distance vertical. The ball traveled a distance of 28 meters and was in the air for 5 seconds. To find velocity horizontal you would divide 5 seconds from 28 meters to get 5.6m/s because the equation is distance over time. To get vertical velocity you multiply 9.8m/s by 2.5 seconds because the acceleration due to gravity is always 9.8m/s. Half the time the ball was in the air was 2.5 seconds. The velocity total was 25.1m/s because the equation a(2)+b(2)=c(2). a= 5.6(2)+b=(24.5)(2)=c(2). 31.36+600.25=c(2). 631.61square root(2). c=25.1m/s. We found that the angle of the projectile being released was 77 degrees. After measuring the spring constant with the spring measuring tool the force came to 80N/m. To find spring potential energy you would use the equation ½(kx(2), after plugging in the numbers it came out to ½(80N/m)(0.4m)(2). Then the equation comes to ½(80N/m)(0.16), multiply those two numbers= ½(12.8N/m) and half of 12.8 is 6.4J. The kinetic energy in the equation is `½(mv)(2) m=mass v=velocity =½(0.007kg)(25.1m/s)(2) = 2.21kgm/s or J. The last calculation we had to find was the vertical distance. The equation was ½(ag)(t)(2), or (9.8m/s)(2)(2.5s)(2). The vertical distance then comes out to 30.625m.
Our secondary experiment tried to figure out if rubber bands or weights were more efficient to launch the projectile. We observed the number of rubber bands and weights and recorded our data to see which went farther and was more consistent. The rubber bands made the ball go further distance than the 1 kg weights. The rubber bands had more tension so the projectile snapped faster than it did with the weights. We couldn’t even test more than 3 of the 1 kg masses because they were so big. The results on how far the ball traveled with each were inconsistent due to other factors and some errors made in the building process. The rubber bands traveled 4m with one rubber band, 10m with two, 11m with three, and 15m with four. The weights didn’t travel as far and the results were very inconsistent but close to each other. With one 1 kg mass the ball traveled at 1m, with two it traveled 5m, and with three it went 4m. We could not test more than three because of the size of the masses. Overall the rubber bands distance consistently increased over time, unlike the weights was inconsistent but increased after more than one weight was added. The weights slowed it down by pulling the arm because they had a big mass. The science shows that using the rubber bands and weights should have the same results, since they both are equal to 10 newtons. In practicality that is not the case. The rubber bands are much smaller and easier to attach than the 1 kg masses and went at least 10m farther. We concluded that the rubber bands are more efficient way to set off the trebuchet.
Our group’s secondary task was to test to see if there was a difference between using weights (1 kg mass) or rubber bands. We thought that the rubber bands would be more effective in propelling the arm of the trebuchet than the weights.
To test this we first attached a nail to the shorter end of the arm. From that nail we were able to attach weights and rubber bands to another nail below that was attached to the board. The next step in testing was to run multiple trials with both the weights and rubber bands increasing the amount and recording the data.
Our data showed something very interesting. Using the spring scale we found out that at its full potential the rubber bands had 10N of force which is also equal to 10000g or 1kg. Of course we were using 1kg masses so that showed us that the rubber bands and the weights had the same exact amount of potential energy. Theoretically they should have had the same exact results on the distance they would be able to fire the projectile, but that was not so. When we fired the rubber bands there was an increase in the meters that the projectile traveled as we increased the amount of bands we attached. With 1 rubber band, it fired the projectile a distance of 4m. With 2, it fired 10m. With 3, 11m and with 4 rubber bands 15m. While the results did not show a linear increase there was a large increase nonetheless. With the weights the results were a little more inconsistent. When using 1 weight the projectile was fired only 1m. With two weights it jumped to 5m, but with three weights it only went 4m, so it traveled less of a distance. Next we tried to put 4 weights on but that was not even possible due to their size.
From those test we were able to conclude that even though the rubber bands and the weights had the same amount of potential energy they clearly did not act the same way. We noticed that the weights seemed to slow the rotation of the arm because of the swinging that took place as they hung on the nail, while the rubber bands had a constant and nonmoving pull. That lead to a faster rotation. There was also a large difference in the size of the two objects. The weights were large and cumbersome and we were not able to get more than three on the arm at any one point. With the rubber bands on the other hand. We were able to put multiple on, increasing the potential energy. From our data there was no end to the amount of rubber bands that we could have put on the machine. In practicality the limit was whenever the wood broke of the nail pulled itself out. For our purposes we only used 5.
Either way our data was skewed and could not be completely relied on due to multiple other factors that could lead to changes. We concluded that the rubber bands were more effective due to their smaller size and being able to attach many more.
The original model had to have an arm, an axle, counterweight, projectile holder, string trigger, hook, and a sturdy base. After some research and experimentation we made some changes. The angle of the nail holding the rubber bands was first, we put the nail in at a 110 degree angle for the most efficiency. The lower angle, the further the ball will fly. At 110 degrees the ball flew 5.95 meters. After that, we altered nail that held the load to the side of the board for more force. Next, we changed was the axle holding the arm in place, the old one we used broke under the pressure of too many rubber bands so we found a new bar. The new bar that we get was one solid piece of wood instead of many, so there was less friction when the arm spinned around. Last, we also changed from weights to rubber bands for creating the force that would project the clay ball. After taking some measurements we discovered that using weights and rubber bands should have the same results since they are both equal to 10N. Theoretically there should have been no difference between the two, but there was. One issue was size. The weights were large and cumbersome while the rubber bands we slim. We were able to get more rubber bands on the arm that weights, creating more force.
We had to find all the calculations of the ball like distance horizontal, time in air, velocity horizontal, velocity vertical, velocity total, release angle of projectile, spring constant, spring potential energy, kinetic energy of the projectile, and distance vertical. The ball traveled a distance of 28 meters and was in the air for 5 seconds. To find velocity horizontal you would divide 5 seconds from 28 meters to get 5.6m/s because the equation is distance over time. To get vertical velocity you multiply 9.8m/s by 2.5 seconds because the acceleration due to gravity is always 9.8m/s. Half the time the ball was in the air was 2.5 seconds. The velocity total was 25.1m/s because the equation a(2)+b(2)=c(2). a= 5.6(2)+b=(24.5)(2)=c(2). 31.36+600.25=c(2). 631.61square root(2). c=25.1m/s. We found that the angle of the projectile being released was 77 degrees. After measuring the spring constant with the spring measuring tool the force came to 80N/m. To find spring potential energy you would use the equation ½(kx(2), after plugging in the numbers it came out to ½(80N/m)(0.4m)(2). Then the equation comes to ½(80N/m)(0.16), multiply those two numbers= ½(12.8N/m) and half of 12.8 is 6.4J. The kinetic energy in the equation is `½(mv)(2) m=mass v=velocity =½(0.007kg)(25.1m/s)(2) = 2.21kgm/s or J. The last calculation we had to find was the vertical distance. The equation was ½(ag)(t)(2), or (9.8m/s)(2)(2.5s)(2). The vertical distance then comes out to 30.625m.
Our secondary experiment tried to figure out if rubber bands or weights were more efficient to launch the projectile. We observed the number of rubber bands and weights and recorded our data to see which went farther and was more consistent. The rubber bands made the ball go further distance than the 1 kg weights. The rubber bands had more tension so the projectile snapped faster than it did with the weights. We couldn’t even test more than 3 of the 1 kg masses because they were so big. The results on how far the ball traveled with each were inconsistent due to other factors and some errors made in the building process. The rubber bands traveled 4m with one rubber band, 10m with two, 11m with three, and 15m with four. The weights didn’t travel as far and the results were very inconsistent but close to each other. With one 1 kg mass the ball traveled at 1m, with two it traveled 5m, and with three it went 4m. We could not test more than three because of the size of the masses. Overall the rubber bands distance consistently increased over time, unlike the weights was inconsistent but increased after more than one weight was added. The weights slowed it down by pulling the arm because they had a big mass. The science shows that using the rubber bands and weights should have the same results, since they both are equal to 10 newtons. In practicality that is not the case. The rubber bands are much smaller and easier to attach than the 1 kg masses and went at least 10m farther. We concluded that the rubber bands are more efficient way to set off the trebuchet.
Our group’s secondary task was to test to see if there was a difference between using weights (1 kg mass) or rubber bands. We thought that the rubber bands would be more effective in propelling the arm of the trebuchet than the weights.
To test this we first attached a nail to the shorter end of the arm. From that nail we were able to attach weights and rubber bands to another nail below that was attached to the board. The next step in testing was to run multiple trials with both the weights and rubber bands increasing the amount and recording the data.
Our data showed something very interesting. Using the spring scale we found out that at its full potential the rubber bands had 10N of force which is also equal to 10000g or 1kg. Of course we were using 1kg masses so that showed us that the rubber bands and the weights had the same exact amount of potential energy. Theoretically they should have had the same exact results on the distance they would be able to fire the projectile, but that was not so. When we fired the rubber bands there was an increase in the meters that the projectile traveled as we increased the amount of bands we attached. With 1 rubber band, it fired the projectile a distance of 4m. With 2, it fired 10m. With 3, 11m and with 4 rubber bands 15m. While the results did not show a linear increase there was a large increase nonetheless. With the weights the results were a little more inconsistent. When using 1 weight the projectile was fired only 1m. With two weights it jumped to 5m, but with three weights it only went 4m, so it traveled less of a distance. Next we tried to put 4 weights on but that was not even possible due to their size.
From those test we were able to conclude that even though the rubber bands and the weights had the same amount of potential energy they clearly did not act the same way. We noticed that the weights seemed to slow the rotation of the arm because of the swinging that took place as they hung on the nail, while the rubber bands had a constant and nonmoving pull. That lead to a faster rotation. There was also a large difference in the size of the two objects. The weights were large and cumbersome and we were not able to get more than three on the arm at any one point. With the rubber bands on the other hand. We were able to put multiple on, increasing the potential energy. From our data there was no end to the amount of rubber bands that we could have put on the machine. In practicality the limit was whenever the wood broke of the nail pulled itself out. For our purposes we only used 5.
Either way our data was skewed and could not be completely relied on due to multiple other factors that could lead to changes. We concluded that the rubber bands were more effective due to their smaller size and being able to attach many more.