Physics Application: Projectile Motion

The projectile is moved in a curved path (poorly drawn, look at energy graph) under the action of gravity. Changing the angle of the trigger will affect the path the balloon will take from a later or early release. 45 degrees gave us the best distance covered changing from 55 degrees with a too early release. The balloon stays at rest until acted upon by the counterweight that moves the arm when the pin is removed. The speed of the arm will equal the speed of the balloon as it is flung through the air. The balloon will stay in motion but then gravity will take affect slowing the balloons momentum through the air. The counterweight is related to the balloons velocity. By adding more weight to the counterweight it could increase the weights speed when projected to the ground also affected by gravity giving it more speed. It will then give the arm a faster fling giving the balloon the same speed.

Physics Application: Energy

As the weight is held in place by the pin the weight contains high amounts of potential energy. This is used to give the balloon the most kinetic energy possible when launched. Adding more height and weight will add more potential energy giving us more built up soon to become kinetic energy for launch which would then improve the distance the balloon would cover. When the balloon is launched all that potential energy becomes kinetic energy but potential energy decreases while kinetic energy increases. At a certain point PE=KE and other points where KE>PE. Once the projectile meets the ground KE=PE again.

Physics Application: Force

Gravity is acted upon the catapult the whole entire time. Frictional force is where our pivotal points are located and can be affected if rust occurs to add more friction. To modify the points to make the rod have less friction in the bearings we can add grease to make it more slick. The smoother the better so there is less traction between the two. We added WD-40 as our substance to make that smooth surface. It will give it more of the fling needed without anything to slow it down much so our balloon can fly as far as it can. While this happens gravity is being acted upon the balloon so adding more weight to our counterweight will give the balloon more of a thrust upward so it can stay in the air as long and cover more distance.

Testing and Modification

First take we got 39 feet by making a sling that cupped the balloon more than hugging the balloon. This would help with the release making sure it would be held too long in the sling. Earlier release would give us better coverage.

Second take we shortened the length of the sling keeping it in the same position and this was actually our best ground covered launch. With 41 feet the earlier release helped by gaining us 2 more feet. Shorter the string the earlier the release which was what we needed.

Third take the sling was re-positioned on the distance from the hook that it is attached but that got us to lose some distance. We lost about 5 feet from our best. It seemed to cup the balloon more so we needed some length between the hook and the sling.

Process of Design and Construction

attempt to cut the frame!

aligning the frame.

We used two four foot steel squared rods ravished from Rani's shed and Matthew's garage for the base. We measured the rods at the two foot mark using a scribe and then cutting at that mark with a power saw. We then cut out corners for the rods so they could meet the two by two feet base requirement. Using a triangle or square we then aligned the rods (four rods were cut out total) for a precise frame and then welded the corners together using a wire fed welder (Hobart handler).

welding has begun!

 

After the frame was welded together we then moved into making the support beams. Two more square shaped rods were found and attached to the sides of the base. The only cutting done were the beams that were set in a triangular shape for optimum support on our main support beams. Same process was used to cut the smaller beams with the power saw and then welded using tack, snake, and booger welds. Some metal parts needed touching so we decided to grind the areas that were needed to be shaved off.

  A hole was made on our arm from a foot length to where the circular rod will go through to hold our arm on the beams. The circular rod then was welded to be part of the arm. We added pillow block bearings to the support beams by adding two holes on each beam using a power drill and screwed on with four bolts and four nuts total. The measurements were made with a measuring tape around two feet from the beams so the arm extended would not exceed five feet total in height. We then took the left over metal and welded it to the base where our trigger mechanism will be located (also drilling another hole in both the arm and the metal beam that would be connected to the arm). A pin was made with an attached string to be placed to hold the arm to the other metal beam.

Log of Meetings

First day of meeting on April 18th: Met for three hours to begin welding on our frame. Members present included Matthew Alvarez and Rani Navicky.

Second day of meeting on May 15th: Met for five hours to add the support beams on the frame including a steel rod through the arm of the catapult. Members present were Matthew Alvarez and Rani Navicky.

Third day of meeting on May 19th: Met for one hour and thirty minutes to add the pillow block bearings on the support beams where we then set our arm in between the two beams. Another rod was placed on other end through the arm where our weights will be added. Members present were Matthew Alvarez and Rani Navicky.

Fourth day of meeting on May 20th: Met for one hour and thirty minutes to add the hook and sling to the arm of the catapult. Members present were Matthew Alvarez and Rani Navicky. Test launches were made later on in the day by Matthew Alvarez.