Science project

The Single Fixed Pulley System


So how does a pulley work? A pulley is one of many simple machines that can make life easier. The pulley you just made is the simplest kind of pulley: a fixed pulley.

In this fixed pulley system, you pull down on one side of the rope and the other side goes up. You use the same amount of force to pull down as you would to lift the toy yourself. However, you have changed the direction of the force.

A fixed pulley is useful because when you pull down, you can use your body’s own weight to add to the push. In contrast, when you exert a force upwards by lifting something, you also have to lift the weight of your own arms. Imagine that you had a small family member sitting on a seat in the air. Would you prefer to lift them overhead with your arms, or hoist them up with a pulley system?

Remember, a fixed pulley changes the direction of the pull, but it doesn’t change the amount of force you use to pull. If you have a very heavy object, you could consider building a moveable pulley. A moveable pulley supports an object with two ropes, placing the pulley in the middle. Since the pulley is being supported by two ropes, the amount of force you need to move an object is cut in half.

Simple machines can make life a lot easier. What other simple machines can you create? Are there others that could help you lift a heavy load? Keep exploring to find out!

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