Rube Goldeberg Edition
Brown, Duong, Menth, Keeler
Simple Machines
Pulleys
Just like a lever, there are three main types of pulleys: the fixed pulley, the movable pulley, and the compound pulley. Pulleys make it easier to lift objects by changing the direction of the force. A pulley is a simple machine, therefore it has a mechanical advantage. The MA formula for pulleys specifically is the input distance or input arm divided by the output distance or output arm. Another way to quickly find the mechanical advantage of a pulley is by using the MA formula for all simple machines: MA=output force divided by input force. A common example of a pulley is a crane.
Single Fixed Pulley
The single fixed pulley is the simplest of the three pulleys. One side of a rope is pulled down, which raises the object that is on the other side of the rope. This pulley changes the direction of the force one exerts by pulling, therefore one can pull down and move an object up. A fixed pulley is used in our project to hold a bucket. That bucket gets filled with marbles and pulls out a board that activates the final stage of our machine.
Below: A single fixed pulley
This single fixed pulley is the only pulley in our machine. It was used to pull out our wedge from its position between two paper funnels.
Compound Pulley
The image on the right is a compound pulley. Compound pulleys are also known as "block and tackle" pulleys. They are a system of several pulleys working together with a single rope that must be pulled to make the system function. This type of pulley reduces the effort needed to lift the load by more than half the weight of the load. The disadvantage to this pulley system is that with more pulleys, the rope has to be a greater length. This means that to move the load a small distance, one must pull a much greater amount of rope, even though it would be easier because less force is required. There are no compound/block-and-tackle pulleys present in our machine.
Movable Pulley
On the left is an image of a movable pulley. Movable pulleys are different from single fixed pulleys because they move with the load and they include multiple pulleys, not just one. Movable pulleys make it so that less effort is used pulling up the load. There is no movable pulley included in our Rube Goldberg machine.
