A pulley is a machine used for lifting or lowering objects. The simplest pulley set-up usually consists of a rope set into a wheel with a grooved rim. When an end of the rope is pulled, the wheel moves, which can in turn move objects or lighten the burden of doing work. The first of these simple machines was likely used in ancient times, but pulleys are still in use today, including in and around the average home.
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The cord pulled to open or close draperies is attached to a pulley system inside of the curtain rod. This pulley makes closing heavy drapes easier because the wheel absorbs most of the force. Similar pulley systems are used to raise and lower window blinds or adjust the blinds to open or closed positions.
Flagpoles contain a pulley system that allows the user to lift and lower the flag. This mechanism is simple, with one fixed pulley wheel at the top of the pole and a fixture to secure the end of the rope at the bottom. Attach the flag to clips at the bottom of the rope and pull the rope downward to allow the pulley wheel to pull the flag up the pole. Although this pulley doesn't decrease the effort required to raise the flag, it does allow the user to reach an area he otherwise could not.
At first glance, a bicycle chain may appear to use a different simple machine; however, the sprockets on a bicycle are only gear-shaped and one is not driven by the force of the other. The chain connecting to a bicycle back wheel uses a pulley to take the motion from one's feet on the pedals and move the wheel forward.
Garage door systems use a pulley similar to the one used on the flagpole. Older garage doors often have the pulley chain inside the garage on one side of the door, and the user pulls down on the chain to pull the garage door open. Battery-powered garage doors use the same pulley principle, but the user no longer needs to perform manual labour to open the door.
Lines used for drying clothes outside often consist of a two-wheel pulley system that spans the backyard. The rope creates a loop with one wheel on each end. The user can begin pinning clothes to the line on one end and pull the rope toward her to move clothes away, creating more space to hang wet laundry.
Dumbwaiters were a common pulley-driven simple machine in older homes. The purpose of this machine was to move items to other floors of the house, like a freight elevator. It was usually used during dinner parties so kitchen staff could send courses upstairs from the kitchen without disrupting the party. The dumbwaiter set-up consisted of a shaft inside the wall with movable pulleys attached to a case that holds items. The case is raised and lowered by pulling the rope threaded through the main pulley.
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