our project is compound pulley system.
Day 1: we simply looked up online of each inventions on the sheet that teacher provided, then we discussed which one is more achievable for us to make, and have the capability to bring or buy the materials
Day 2: we start building up our project with all the materials I brought from home. We decided to use thread rolls as pulleys, and thread as ropes. At jut the first few steps, we got obstacles. How could the thin thread rolling the pulleys if the “pulleys” are too big for it? Through a long time thinking and discussion, we finally figured out what should we do on next day, and what additional materials we need to bring. For example, should we use the third thread roll as load? How should we keep all the pulleys balanced while it’s rolling? Etc.
Day 3: When we realized what was our problem, I came up a solution which is we should use a tall object to be act as pillar, such as a water bottle(though we replaced with bottle of potato chips at last). The purpose of using that is to establish the fixed pulley, so that the whole system has a ending point. Hence we using long ruler(we replaced it with wood board later on) as “celling”, therefore we can stick the rope and fixed pulley on it. Secondly, I got an idea which is use tape to make a little hole on the surface of thread roll (the one act as movable pulley) that could let thread go through it and without lost balance. It did work. Here all problems seems fixed, but the movable pulley did not cooperate very well. When I pulling rope, it did not rolling at all. At first we thought because the edge of thread roll is too rough. Even though we use paper cover all the edge, it is still not work very well, only seldom rolled.
In general, this object was not as easy as I thought before I started. However, I am very glad that my partner kept trying new things, and we have discussions to solve all the difficulties, which is a great help to let this project done perfectly on time.
Archimedes was the first person who point the statement out, make greatly contribution to help people understand the pulley, even though he did not invent any machines of that. Archimedes was the first person documented block and tackle pulley system.
Pulley system was firstly used in water-lifting, people found this method highly improved the efficiency of the force use, and save the amount of force need to apply on the object. This type invention was formally discovered in 1500 b.c. in Mesopotamia area, but at that time they were still using single pulley system. However, about 400 b.c. The Greeks had put to use compound pulleys, or ones that contained several wheels. Plutarch, the Ancient Greek philosopher who developed and invented a pulley machine based on theory of Archimedes. That was known as the Claw of Archimedes, also known as “iron hand”.
Nowadays, compound pulley systems would find application in many things aroun us such as elevators and escalators, also in some theatres still use this system to fly actors.
Description of physics involved in your machine:
Physics involved: In a compound pulley system, it included at least one fixed pulley and one movable pulley. One fixed pulley system would not save force, but it changed the direction of force which convenient the people to contribute force. On the contrary, the movable pulley system can save half force while pulling things up. However, if combined them together, the entire pulley system can saved totally half force. In addition, as you increase the number of the ropes that surround the pulleys, it saved more force. This is a consequence of the tension in any rope is constant, the tension on a rope in a pulley system is the total forcée divided by the number of sections of rope pulling up the mass.
mathematics examples: Due to the compound pulley system uses the work-engery principle. The principle is “work is done by a force(F) pushing over some distance(s). The θ is the angle between the force and the displacement.”