How to distinguish between movable pulley and fixed pulley? 10

Fixed pulley A pulley with a fixed position, when the wheel rotates and the position of the entire pulley remains unchanged. This pulley can only change the direction of the force and does not save effort. Movable pulley The pulley whose position is not fixed, and the entire pulley is displaced when used.

Effort can be saved by using this pulley. Singlely, when the pulley block is working, it is the moving pulley that rises or falls with the rope, and the rope moves but the pulley does not rise or fall is the fixed pulley (the fixed pulley will do a circular rotation, but the position is not moving. A pulley in which the position of the shaft moves with the object being pulled is called a movable pulley.

It is a deformed unequal arm lever that saves half the force (without considering the gravity and friction of the object), but does not change the direction of the force. Human supplement 2009-08-25 17:47 The fixed pulley is essentially an equal arm lever, and the power arm L1 and the resistance arm L2 are equal to the radius of the pulley.

According to the lever balance conditions, it can also be concluded that the fixed pulley is not labor-saving or labor-saving.

Like the pulley at the top of the flagpole, a pulley that rotates in one position without moving is called a set pulley.

Fixed pulleys and movable pulleys are essentially lever principles (in fact, it is a matter of moment balance, but you should not have learned it, so it is easier to understand levers).

The fixed pulley takes the center as the fulcrum, and any radius is the force arm, and the reason why it can be pulled in any direction without the same force size is because the length of the force arm is unchanged.

And the movable pulley takes the intersection of the fixed rope and the pulley as the fulcrum, which is the moving fulcrum, then the force arm of the pulley gravity to the fulcrum is the radius, and the gravity is vertically downward, so the force and the force arm product is not the same as gr, the reason why the vertical upward pulling force is the smallest is because the force arm of the pull force is the diameter d at this time, so the force is exactly half of the gravity, if it is pulled in other directions, because the force arm is less than d, so the force is large.

In use, the height of the pulley has always remained the same is the fixed pulley, and the pulley also moves up and down with the object moving up and down is the movable pulley.

The movable pulley can change direction and can also save effort. The fixed pulley can only save effort.

The moving pulley can be regarded as shaking the empty bamboo in the bamboo, raising the national flag, and the thing at the top of the flagpole that changes the direction of the rope is the fixed pulley.

The central axis of the fixed pulley is generally fixed to the wall, and there is nothing in the center of the movable pulley to fix it.

The fixed pulley is generally hung on the ceiling or wall...

The rest should be movable pulleys...

Fixed pulley: fixed in one place, can not move with the movement of heavy objects.

Movable pulley: not fixed, can move with the movement of heavy objects.

Features: 1. Fixed pulley.

The fixed pulley is a kind of fixed pulley, its fixation is not simply fixed, but the central axis of the pulley is fixed, the main advantage of the fixed pulley is that it can change the direction of the force, when we use the fixed pulley to pull a very heavy object, it is not very hard.

2. a movable pulley.

The use of movable pulley can save half of the force, the distance, this is because when using the movable pulley, the hook code is hung by two sections of rope, each section of the rope only bears half of the weight of the hook code, although the use of the movable pulley saves force, but the distance of the power movement is 2 times the distance of the hook code elevated, that is, the distance.

See the diagram below: <>

Labor-saving calculations. Formula: s = nh, v rope = n * v matter f pull = (1 n) * g total.

s: The distance traveled by the free end of the rope. V-rope: The speed at which the free end of the rope moves (ascends, descends).

h: The height at which the weight is lifted. v-object: The speed at which an object moves (rises, falls).

n: The number of load-bearing rope segments (rope connected to the movable pulley). G total: weight + pulley weight (G object + G slip).

Secondly, determine the number of fixed pulleys according to the requirements, and the principle is: general: two strands of rope with a movable pulley.

The difference between fixed pulley and movable pulley: fixed pulley is fixed, that is, its position will not change; The movable pulley moves along with the object being pulled up. The fixed pulley is not labor-saving, but it can change the direction of tension; The movable pulley saves effort, but it cannot change the direction of the force.

The fixed pulley is a kind of fixed pulley, and its fixation is not simply fixed, but the central axis of the pulley is fixed. The main advantage of the fixed pulley is that it can change the direction of the force, and when we use the fixed pulley to pull a very heavy object, it is not very forceful.

But we can change the direction of the force to the direction that we can use very well with a fixed pulley, so that it is easy to pull the weight. The disadvantage of fixed pulley is that it cannot save effort.

The use of movable pulleys can save half of the effort and distance. This is because when using movable pulleys, the hook is suspended by two sections of rope, each of which bears only half the weight of the hook. Although the use of movable pulleys saves force, the distance of power movement is twice the distance raised by the hook code, that is, the distance movable pulley cannot change the direction of force.

Moves as the object moves. In addition, the quality of the movable pulley itself cannot be ignored in life, so extra work is done in the process of the movable pulley rising to reduce the mechanical efficiency.

Pulley Introduction:

The pulley is a very easy thing for us to see, it is actually a simple machine, which can help people complete some simple mechanical operations. The structure of the pulley is also relatively simple, it is mainly composed of a central shaft and small wheels with small grooves around the perimeter, and is equipped with wire ropes, chains and tapes.

The reason why the pulley slides so easily is mainly because of its small wheel and the central shaft. There are also many materials used to make pulleys, such as plastic, wood, and steel. The role of the pulley is great, and we often have to rely on the pulley to complete some necessary operations.

For example, the transmission of heavy objects or the need to change the direction of the force are all done by pulleys.

How to distinguish between fixed and movable pulleys:

1. Fixed pulley

The fixed pulley, also known as the fixed pulley, is mainly used to change the direction of movement of the towing rope or chain. The common fixed pulley has a fixed shaft and a fixed pulley, which is fixed in the machine or equipment as a whole. It is characterized by its ability to be stably fixed in one place and to change the direction of movement of the rope or chain by frictionless sliding.

The fixed pulley cannot change the speed of movement of the rope or chain, it only changes the direction of its movement. Therefore, fixed pulleys are usually used in situations where the direction of motion needs to be changed without changing the speed of motion.

2. Movable pulley

The movable pulley, also known as the movable pulley, is characterized by the fact that it can change both the direction of movement of the rope or chain and the speed of its movement. A movable pulley usually has two wheels, one of which is fixed and the other is movable. In addition, the movable pulley has two parts:

Brackets and movable pulleys.

The bracket is a metal frame fixed in a fixed position, usually welded from steel plates, and the function of the bracket is to support the movable pulley and bear its load, ensuring that it can rotate and slide freely.

The movable pulley is located in ** and usually consists of a special axle, disc and teeth. Teeth are usually designed in a V-shaped or rounded shape for a good bond with the rope or chain. The movable pulley can be operated by switches, motors, or direct human labor.

By changing the position of the pulley, the speed of movement of the rope or chain can be increased or slowed down.

3. Occasions and precautions for the use of fixed pulleys and movable pulleys

1. Occasions and precautions for the use of fixed pulleys:

Fixed pulleys are usually used when changing the direction of motion of ropes or chains, such as cranes, cranes, etc.

Attention should be paid to the following matters in the use of fixed pulleys:

1) Wheels should be selected that are appropriate to the diameter of the rope or chain.

2) Attention should be paid to the quality of the wheels and the manufacturing process to ensure frictionless operation, 3) Attention should be paid to the installation position between the wheels and the fixing hook or bracket to ensure fixation and stability;

4) Attention should be paid to selecting the appropriate fixed suspension position in order to meet the required traction force.

2. Occasions and precautions for the use of movable pulleys:

Movable pulleys are usually used in situations where the direction and speed of motion of ropes or chains need to be changed, such as automobiles, railways, and machinery manufacturing.

The following things need to be paid attention to when using movable pulleys:

1) Wheels with suitable rope or chain diameter should be selected;

2) Attention should be paid to the quality and manufacturing process of the gear teeth to avoid the tooth sliding;

3) Attention should be paid to the selection of appropriate brackets and movable pulleys to ensure the stability of their movements, and 4) the position of the movable pulleys should be adjusted according to the needs to change the speed of movement.

In short, fixed pulleys and movable pulleys have their own advantages, and they have good application prospects in different occasions. It is necessary to choose the right pulley according to different needs.

The differences are as follows:

The central axis of the fixed pulley is fixed, and the function of the fixed pulley is to change the direction of the force, but it can not save the force, when pulling the heavy object, the fixed pulley can be used to change the direction of force to the direction of easy force. When using a fixed pulley, the distance of force pulling is equal to the distance of the object rising, the tensile force at both ends of the rope is equal, the output force is equal to the input force, and the mechanical efficiency of the fixed pulley is close to 1 when the friction is not counted.

The movable pulley is the pulley that the position of the shaft moves with the pulled object, and the movable pulley is essentially the lever of the power arm equal to 2 times the resistance arm is usually the force-saving lever, which can not change the direction of the force, and can save up to half of the force at the same time, but it does not save the work, and is usually used in daily life with the fixed pulley to form a pulley group.

The difference between the fixed pulley and the movable pulley is that the movable pulley can change the direction of the force and save more effort at the same time, while the fixed pulley can make the mechanical efficiency approach to 1 while changing the direction of the force, which is more labor-saving. The two are often used in combination in life.

In mechanics, a typical pulley is a round wheel that rotates around a central axis. There is a groove on the circumferential surface of the wheel, and the rope is wound around the groove, and either end of the rope is pulled forcefully, and the friction between the rope and the wheel will cause the wheel to rotate around the central axis.

A pulley is actually a deformed, rotating lever. The main function of the pulley is to pull the load, change the direction of force, transmit power and so on. The machine that is composed of multiple pulleys together is called a "pulley block", or "compound pulley".

The mechanical benefits of the block are greater and can pull heavier loads. Pulleys can also be a chain drive or belt drive component, transferring power from one rotating shaft to another.

According to whether the position of the central axis of the pulley moves, the pulley can be divided into "fixed pulley" and "movable pulley"; The central axis of the fixed pulley is fixed, and the central axis of the movable pulley can be moved, each with its own advantages and disadvantages. And the fixed pulley and the movable pulley are assembled together to form a pulley block, which not only saves force but also can change the direction of force.

The pulley appears in the form of knowledge points in junior high school physics textbooks, which requires answers to questions such as the direction of force, the distance of rope end movement, and the work done.