what is a pulley

A pulley is a simple machine used to lift heavy objects and save effort. A pulley is a small wheel with grooves around it that can rotate around an axis. A simple machine that can rotate around a central axis, consisting of a grooved disc that can rotate around a central axis and a flexible cable (rope, tape, cable, chain, etc.) that spans the disc, is called a pulley.

In mechanics, a typical pulley is a round wheel that rotates around a central axis. There is a groove on the circumference of the round wheel, and the rope is wound around the groove, and either end of the two ends of the rope is pulled hard, and the friction between the rope and the round wheel will cause the round wheel to rotate around the central axis. Pulleys are actually deformed, turning levers. The main function of the pulley is to pull the load, change the direction of the applied force, transmit power and so on. A machine composed of multiple pulleys is called a "pulley block", or a "complex pulley". The pulley block has greater mechanical advantage and can pull heavier loads. A pulley can also be a component of a chain or belt drive that transmits power from one rotating shaft to another.

According to whether the position of the center axis of the pulley moves, the pulley can be divided into "fixed pulley" and "moving pulley". The center axis of the fixed pulley is fixed, and the center axis of the movable pulley can move. Each has its own advantages and disadvantages. The fixed pulley and the movable pulley can be assembled together to form a pulley block. The pulley block not only saves effort but also can change the direction of force.Pulleys appear in the form of knowledge points in junior high school physics textbooks, requiring answers to questions such as the direction of force, the moving distance of the rope end, and the work done.

The principle and characteristics of the fixed pulley

When using a pulley, the pulley whose shaft position is fixed is called a fixed pulley.

When in use, the position of the pulley is fixed; the fixed pulley is essentially an equal-arm lever, which does not save effort or effort, but it can change the direction of the force. The power arm and resistance arm of the lever are the radius of the pulley respectively. Since the radii are equal, the power The arm is equal to the resistance arm, and the lever is neither effort nor effort.

The fixed pulley cannot save effort, and when the weight of the rope and the friction between the rope and the wheel are ignored, no matter where the force direction of the thin rope is, the force used to lift the heavy object is equal, because the power arm and the resistance arm are both Equal and equal to the radius of the pulley.

The principle and characteristics of movable pulley

Definition 1: When a pulley is used, the pulley whose axis moves with the object being pulled is called a moving pulley. Definition 2: If the heavy object is directly hung on the pulley, the pulley will also rise together when the heavy object is lifted, such a pulley is called a moving pulley.

principle

The movable pulley saves 1/2 of the force and doubles the distance. This is because when using the movable pulley, the hook is suspended by two ropes, and each rope 

only bears half of the weight of the hook, and the direction of the force cannot be changed.

According to the principle that any machine does not save work, we have (s1 is the moving distance of the free end of the rope, s2 is the moving distance of the object

, which can also be understood as the lifting distance of the object without machinery):

attention to pulleys

The movable pulley saves 1/2 of the force and doubles the distance, and it is limited to vertical upward force. The greater the angle of force tilt, the more force is used. 

And when using a movable pulley, the weight of the pulley also affects the force used. When the gravity of the pulley is not ignored and the force is exerted vertically 

upwards, we have: F=(G wheel+G object)/2

What is a pulley block

Pulley Block: A pulley device consisting of a fixed pulley and a movable pulley. It saves effort and can change the direction of force. But it cannot save effort, because the

 pulley block saves effort, but costs distance. In order to save money and change the direction of power, the fixed pulley and the movable pulley can be combined into a

 pulley block.

Link-B2B is a professional supplier listing service platform which will provide high quality and trustworthy supplier list to international buyers. If you are looking for pulley suppliers, feel free to visit Link-B2B.com and send a request.