What Is a Pulley?
A pulley is a simple machine. It is a wheel with a groove, and a rope runs over the wheel. When we pull one end of the rope down, the load on the other end goes up.
How a Pulley Helps
A pulley makes it easier to lift a load. Instead of pulling a heavy load straight up, we can pull the rope down, which is easier because we can use our own body weight. A pulley also lets us lift a load to a high place, like raising a flag up a pole or lifting a pail of water from a well.
Key idea / 要点
A pulley is a wheel with a rope that helps us lift a load more easily by pulling the rope downwards.
Example / 例子
To raise the school flag, we pull the rope down. The pulley at the top of the pole lets the flag go up easily.