A pulley is a simple machine made of a rope or chain wrapped around a wheel. There can be grooves along the edges to guide the rope or chain. It has two raised edges so that a rope or a string will run along the wheel without coming off. Pulleys are often used to pull rope with greater ease, change the direction of a force, or to get more mechanical advantage and lift something you wouldn’t otherwise be able to by yourself.
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Watch this short video explanation of a pulley. It explains the advantages of using a single pulley as well as a system of pulleys. Note the examples used in this clip. |
A pulley that is attached to a hook or a wall and doesn't move is called a fixed pulley. Think of a clothesline. This fixed pulley doesn't give you any mechanical advantage, but it changes the direction of the force. For example, you can pull the upper part of clothesline toward you in order to move the lower portion away from you. Or, in cases other than clotheslines, you can pull down on the rope in order to lift something up, like when using a well to gather water.
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Another type of pulley is a moveable pulley. These pulleys do have a mechanical advantage in that they decrease the amount of effort required to lift the load, but you have to apply the force for a longer period of time in order to move the intended object/objects.
Take a look at the link attached below. On this site you will find some interesting uses for pulleys as well as some fun facts about this simple machine.
Watch the video linked below. This will provide you with a simple explanation of a pulley and how adding pulley wheels creates more of a mechanical advantage.
Pulleys do some very important work. Watch the video below to see how pulleys work to help NASA raise and lower the space shuttle before and after flight!
Pulleys do some very important work. Watch the video below to see how pulleys work to help NASA raise and lower the space shuttle before and after flight!
Let's take a look at how we use pulleys in our everyday lives. Can you imagine how life might be different without some of these mechanisms?
Please see Simple Machine Activities under the Content Activities drop down menu or click the link below to complete your end-of-chapter assignments: