Concrete Boat Project
For our last project in Advanced Physics, we were tasked with building boats out of concrete that float for at least 10 seconds. The catch: we have to put a Barbie doll in the boat and still have it float. My partner and I decided to build ours off of a bowl mold. We thought that a cooking bowl with a wide rim that gently curved down to the bottom would provide the best surface area and buoyancy to weight ratio. Then we had to find the volume of our bowl, which was hard because we had to calculate two caps and then subtract one from the other. Using the volume and mass of the boat we were able to determine the percentage of our boat that would be below the water. From this we were able to find out if our boat was going to float or not.
Trebuchet Project
We built a website to exhibit our trebuchet, which can be found here:
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Project Reflection
I would most definitely have made the same contraption if given the choice to do this project over.. I liked our design and how it used math to deliver more power to the sling.
I think that if I were to build my trebuchet again, I would have scaled it up a little bit. Our throwing arm was one fourth the length of our competitions’. I think that if we had built ours a little bigger, we would have been able to fire farther and use heavier weights. I also would have built a different sling. Each of our shots was at a different angle, without our sling being changed between shots. I think that if we were to dynamically tune the sling, we could get our pumpkins to shoot a lot farther.
I think that we were losing power into the inefficiency of the top axle. We never greased the pipe inside of the PVC and it made an awful noise when we would spin it. The friction of the PVC rotating around the ungreased metal pipe created heat and sapped energy from the arm. Another place I think we were losing energy was in the the slight bounce of the rope as it unwound, as seen in the video footage. It was slight, but I think that it may have thrown the rope off just slightly, resulting in a loss of power. Another place I think we were losing power was when the sling was released. It wouldn’t open correctly and the pumpkin would shoot down or backwards.
I was really happy with my group. Dylan and I were good at getting the pieces cut, we were all good at putting the thing together and I think we shared the work equally. If I were to go back and do it all over again, I would absolutely choose the same group.
I would say our contraption was about 80% optimized. Our arm and weight system worked every single time. Our only issue was getting the sling to release properly. I think that if we were able to get our sling to work optimally, we could have got our pumpkin to launch about as far as the traditional trebuchet. We were able to achieve this distance once, but were unable to repeat the feat in the competition.
I think we had most of the right materials. Our throwing arm was really skinny, but made of hard oak, and I think we could have picked bigger lumber to use there. We used a burlap sack for our sling and I think we could have used a better material for that. Maybe a net of some sort. Other than that, I think we had all the right materials for the job. We even had extra lumber left over, which was not common between the groups.
Well we didn’t scale our contraption up enough so we had a smaller build. We had to use the smallest pumpkins we could get our hands on, but once we got them, they were perfect for our trebuchet.
I think that this was a fair competition. Everybody was given the same amount of lumber at the beginning and the same amount of time to build it. In the end, everybody should have had a working device to present. However, there were some groups that chose designs that were inherently more complicated than others. Since some designs were easy to make they were done in a week while others took much longer to complete. In that sense it wasn’t quite fair but I don’t know how that would be remedied.
My advice to next years students would be to pick a design that you know you can do. The last thing you want is some contraption that half works and half doesn’t while other kids are happily shooting their less complicated designs. And if you do choose a design that is complicated, be sure that you are willing to put in the time to make it happen.
I would most definitely have made the same contraption if given the choice to do this project over.. I liked our design and how it used math to deliver more power to the sling.
I think that if I were to build my trebuchet again, I would have scaled it up a little bit. Our throwing arm was one fourth the length of our competitions’. I think that if we had built ours a little bigger, we would have been able to fire farther and use heavier weights. I also would have built a different sling. Each of our shots was at a different angle, without our sling being changed between shots. I think that if we were to dynamically tune the sling, we could get our pumpkins to shoot a lot farther.
I think that we were losing power into the inefficiency of the top axle. We never greased the pipe inside of the PVC and it made an awful noise when we would spin it. The friction of the PVC rotating around the ungreased metal pipe created heat and sapped energy from the arm. Another place I think we were losing energy was in the the slight bounce of the rope as it unwound, as seen in the video footage. It was slight, but I think that it may have thrown the rope off just slightly, resulting in a loss of power. Another place I think we were losing power was when the sling was released. It wouldn’t open correctly and the pumpkin would shoot down or backwards.
I was really happy with my group. Dylan and I were good at getting the pieces cut, we were all good at putting the thing together and I think we shared the work equally. If I were to go back and do it all over again, I would absolutely choose the same group.
I would say our contraption was about 80% optimized. Our arm and weight system worked every single time. Our only issue was getting the sling to release properly. I think that if we were able to get our sling to work optimally, we could have got our pumpkin to launch about as far as the traditional trebuchet. We were able to achieve this distance once, but were unable to repeat the feat in the competition.
I think we had most of the right materials. Our throwing arm was really skinny, but made of hard oak, and I think we could have picked bigger lumber to use there. We used a burlap sack for our sling and I think we could have used a better material for that. Maybe a net of some sort. Other than that, I think we had all the right materials for the job. We even had extra lumber left over, which was not common between the groups.
Well we didn’t scale our contraption up enough so we had a smaller build. We had to use the smallest pumpkins we could get our hands on, but once we got them, they were perfect for our trebuchet.
I think that this was a fair competition. Everybody was given the same amount of lumber at the beginning and the same amount of time to build it. In the end, everybody should have had a working device to present. However, there were some groups that chose designs that were inherently more complicated than others. Since some designs were easy to make they were done in a week while others took much longer to complete. In that sense it wasn’t quite fair but I don’t know how that would be remedied.
My advice to next years students would be to pick a design that you know you can do. The last thing you want is some contraption that half works and half doesn’t while other kids are happily shooting their less complicated designs. And if you do choose a design that is complicated, be sure that you are willing to put in the time to make it happen.