A pulley is a simple machine made with the help of a grooved wheel and a rope, a wire, or a chain. It is one of the oldest machines and was first introduced in 1500 B.C. by the people of Mesopotamia. In a pulley mechanism, the load is attached to one end of the rope and the force is applied to the other end. The applied force is responsible for either lifting or lowering the load. As the name suggests, a pulley mechanism is used to pull or lift objects with ease. Back in the old times, the original task of a pulley was to lift heavy objects such as a bucket filled with water; however, in the present world, a wide range of daily life and commercial applications make use of the pulley system. Depending on the type of application, the pulley system can have a fixed axle, a movable axle, or a combination of both.
Examples of Pulley Simple Machines
Wells are one of the oldest applications that make use of a pulley. To draw water from a well, the handle of the bucket is tied with one end of the rope and is thrown in the well. The other end of the rope is given to the user who applies pull force to it. The bucket filled with water that is pulled via the axle of the movable pulley reduces the amount of input force and the water is extracted out with ease.
The greatest application of a pulley mechanism in the engineering domain lies in the construction of elevators. The elevators/lift make use of highly tensile ropes that help to move it up and down as per the user requirement. In absence of a pulley, a complex arrangement of heavy motors is required to pull the cables and thereby causing the lift to move.
3. Exercise Equipment
A number of gym and exercise equipment consist of a rope that is attached with weights on one end; whereas, the other end of the rope passes over the pulley and is given to the consumer. When the user pulls the leisure end of the rope, the force gets transferred to the user’s body helping him/her to strengthen the muscles. Most of the cable machines used in athletic training centres for example a seated cable row employ a cable-pulley arrangement and are commonly referred to as pulley machines.
4. Theatre Curtains
Unlike regular curtains, a theatre curtain is not pulled manually. A separate mechanism is used that helps the user to roll and unroll the theatre curtains with the help of a cord. When the cord is pulled down the curtains get lifted up with the help of a pulley mechanism. Here, the pulley is used for the purpose of reducing the efforts required to draw the curtains on or off the stage.
5. Construction Equipment
A pulley mechanism helps the lifting of heavy objects much easier as compared to picking up the weight manually. Hence, it is most frequently used in construction equipment that requires lifting and dumping of hefty and bulky objects. Some of the construction machines that make use of a pulley mechanism are cranes, a gun tackle, a yard and stay tackle, etc.
Flag poles are usually very tall, which makes flag hoisting a very difficult job to be done manually. However, if a mechanism of a rope and pulley is used to do the task, it becomes easy and seems effortless. To unfurl a flag on a flagpole with the help of pulleys, a user attaches the rope with the flag and pulls the rope. When the rope attached to the top of the pole is pulled via a pulley wheel it causes the flag to go up.
Blinds used on a window move up and down very smoothly. A simple pulley machine is used to serve the purpose. The cord of the blind is attached to the axle wheel of a pulley. Hence, when the cord is pulled, the pulley causes the blinds to go up.
8. Rock Climbers
A rock climber uses a pulley mechanism to ease the process of climbing. A pulley mechanism is usually used to divert or change the direction in which the force is applied. As the climber pulls the rope in the downward direction, the pulley system helps him/her to move in the upward direction.
9. Garage Doors
A garage door is quite bulky and heavy, which is why it is difficult to be operated manually. To make this process easier, a set of four pulleys is attached to the top corners of the garage door. These pulleys are connected via a low mass string that helps the door to move up and down smoothly.
10. Sails on Sailboat
Sailboats and ships make use of a single pulley or a mechanism of multiple pulleys to lift heavy sails and cargo. This is done by a simple rope that is pulled downward causing the heavyweight present on the other end to get lifted up. To further ease this process, the pulley used consists of ball bearings. Thereby, ensuring smooth sailing.