What is A Pulley?
So far we have been looking at different kinds of pulley systems. Can you remember which ones they are?
!?Did You Know?!
A pulley is a simple machine. It is a variation of a wheel. A rope or cable passes back and forth over one or more grooved wheels.
One end of the rope is attached to the load, and the other end is pulled in order to move or lift the load. The pulley makes the task less work, because it is easier to pull a rope down than it is to lift the weight up.
A simple pulley has only one wheel. This pulley changes the direction of a force but does not magnify the force.
Fixed pulley: A fixed pulley is a pulley that is attached to a fixed structure above the load being lifted. A fixed pulley adds no mechanical advantage to lifting a load, but they do change the direction of applied force, which is useful if the load is in an inconvenient spot.
A single fixed pulley can be used to change only the direction of the applied force. However, a movable pulley can be used to decrease the input force required.
Moveable Pulley: Is when there is a pulley attached to the load being lifted. The pulley is free to move up and down along with the load
In the next few classes we will be looking at Compound Pulleys.
A Compound pulley is a system that uses more than one pulley to lift or move a load. The more pulleys in the system, the greater the mechanical advantage.
The Block and Tackle is an example of a compound pulley, where one set of pulleys is fixed (to a ceiling for example) and the second set of pulleys is attached to the load being lifted.