Raheel+&+Ali

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Floating Arm Trebuchet
If you can't lead by example, intimidate



=** Introduction **= The trebuchet derives from the ancient sling. This evolved into the traction trebuchet by the Chinese, in which a number of people pull on ropes attached to the short arm of a lever that has a sling on the long arm. The smallest traction trebuchets could be powered by the weight and pulling strength of one person using a single rope, but most were designed and sized for 16 to 46 men, generally two per rope. These teams would sometimes be local citizens helping in the siege or in the defence of their town. Traction trebuchets had a range of 100 to 200 feet when casting weights up to 250 pounds. The purpose of this project is to design an efficient trebuchet, capable of throwing a 5g Christmas ornaments. The efficiency of our trebuchet is determined by the formula Distance (m)/(Length of the arm(m) * Mass of the trebuchet (kg))   A floating-arm trebuchet is a modern variant of a trebuchet. The main difference is that rather than having an axle fixed to the frame, the axle is mounted on wheels that roll on a track parallel to the ground. This results in the counterweight moving in a direct path downwards upon the release, which increases the energy transferred to the projectile, making it more efficient. More often, the counterweight is actually constrained to fall vertically by forcing it to fall in a vertical slot, thus ensuring that there is no to-and-fro movement of it during any part of the throw.
 * Our Trebuchet (Floating Arm Trebuchet)**

2. Gravity: Refers to the force exerted by an object with mass which attracts another object. If there was no gravity, everyone in the physics class would get a 100% (therefore everyone would be happy) since the Christmas balls would go an infinite distance (Unless they hit a wall or something). 3. Kinetic Energy: Refers to the extra energy obtained by an object due to it's movement. We made a floating arm trebuchet and one of the advantages our trebuchet had over the classical trebuchets was the addition of wheels to the arm. The wheels convert the kinetic energy of the falling weights into an extra amount of force exerted on the object being thrown. 4. Newton's Second Law (F=ma): Force equals mass times acceleration. The projectile has mass, gravity and the floating arm adds acceleration therefore you get a certain amount of force. 5. Centripetal Force: Is a force that makes a body follow a curved path; it is always directed orthogonal to the velocity of the body, toward the instantaneous center of curvature of the path. 6. Newton's first law: An object at rest tends to stay at rest and an object in motion tends to stay in motion with the same speed and the same direction unless acted upon by an unbalanced force. This applies to our trebuchet, since when the arms stops, the ball continues to move forward. 7.Friction: The force opposing the direction of the movement of an object. This applied to our trebuchet since after sanding the tracks and reducing friction, the wheels rolled much faster.  = = =Procedure= Start by making the base. Use two 4 inch planks and glue them on to the ends of the two 12 inch planks making sure they are perpendicular to the base. Then use two more two 12 inch planks, these will be one side of the track where the weight bar will slide. Glue those to the center of the base making sure to leave a small gap just big enough for the bar to have a little wiggle room. Next, make the track where the wheels roll. Measured the distance from the 4 inch plank to the 12 inch plank vertical making sure not to overlap on to the track where the bar passes. An identical board should be made for the rest of the track on this side of the frame and both should be glued parallel to and on the same side of the verticals as the base board. The other side is made the same way. For the throwing arm use another 12 inch plank. Finally, attach wheels and the weights to the throwing arm, use the 2.5 inch metal rod to put the wheels on the arm. Put the 14 inch rod on about two inches from the bottom of the arm. The only thing left to do is to put the two sides of the trebuchet together making sure to give the wheels just enough clearance.
 * Applied Physics** 1. Projectile Motion: A projectile is any body that is given an initial velocity and then follows a path determined by the effect of the gravitational acceleration and by air resistance. The Christmas ball we lunched is a perfect example of projectile motion, since after it is lunched the only forces acting on it are gravity and air resistance.
 * Materials**
 * 4" wooden plank x 8
 * 12" wooden plank x 8
 * Wood glue
 * 10 wooden wheels (8 as counterweights, and 2 for the floating arm as wheels)
 * One 2.5" metal rod
 * One 14" metal rod
 * Miter saw



We tested our trebuchet with different counterweights. First we started with two 45 grams wooden wheels on each side, and went up to 450 grams of counterweight on each side. We found out that the best P score would be achieved with 4 wooden wheels on each side. Then we adjusted the length of the loop. We found out a smaller loop would give us a higher P score. Having found the perfect arm length and counterweight we tested our trebuchet eight times, and recorded the results in the table below.
 * Testing Procedure:**

 **Test Results:** We made three trebuchets out of which two did not even work. We started working on the first one on Dec 5th, and finished it on Dec 6th. It was made out of popsicle sticks but unfortunately it failed. On Tuesday, Dec 8th we started working on two floating arm trebuchets. One of them was made out of 8 and 24 inch planks of wood, and the other one out of 4 and 12 inch planks of wood (So, this one is half the size of the other one). We thought we would make the small one just for fun, but it actually saved our butts since we finished both of the floating arm trebuchets on Dec 10th at 7:00 P.M. and the bigger one failed to work. After working on the smaller trebuchet for 2 hours, we finally got it to work properly, but it was giving us a P score of 4.5. After working on it for three more hours we manage to achieve a P score of 11.
 * Trial || Mass (kg) || Arm (m) || Distance (m) || P = d/ml ||
 * 1 || 1.6 || .31 || 6.14 || 12.38 ||
 * 2 || 1.6 || .31 || 6.26 || 12.62 ||
 * 3 || 1.6 || .31 || 6.23 || 12.56 ||
 * 4 || 1.6 || .31 || 6.17 || 12.44 ||
 * 5 || 1.6 || .31 || 5.99 || 12.08 ||
 * 6 || 1.6 || .31 || 6.30 || 12.70 ||
 * 7 || 1.6 || .31 || 5.94 || 11.97 ||
 * 8 || 1.6 || .31 || 6.35 || 12.80 ||
 * Average || 1.6 || .31 || 6.18 || 12.44 ||
 * Friday (Dec 11th) || 1.6 || .31 || 5.98 || 12.06 ||
 * Analysis**
 * We wanted a short arm, therefore we decided not to add a sling to the arm. (The sling brought our P score down)
 * We sanded the tracks where the wheels rolled in order to reduce friction.
 * We spent close to an hour just to find the perfect counterweight.
 * We used light, cheap wood, for the project, so the main weight came from the metal rods and the counter-weights we used.
 * We tied a string to a Christmas ball and made a small loop with it. Then hung the loop on a niddle attached to the end of the arm; therefore the ball and the string would go flying at the same time. Using this type of sling, the length of our arm was reduced, and the ball actually went farther.