Function and characteristics of labor-saving prono

2022-07-22
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The painting of pulley first appeared in an Assyrian relief in the 8th century BC. This relief shows a very simple pulley, which can only change the direction of force application. The main purpose is to facilitate force application, and will not give any mechanical benefits. In China, the drawing of pulley device first appeared in the portrait bricks and pottery well models of the Han Dynasty. There are also discussions about pulleys recorded in the Mojing

The pulley whose position of the shaft moves with the object being pulled is called a moving pulley. The movable pulley is essentially a lever with a power arm equal to twice the resistance arm. It cannot change the direction of the force, but it can save half the force, but it does not save work. The fixed pulley can form a pulley block. It is a simple machine commonly used in daily life. Now let's introduce the function and characteristics of the movable pulley. Let's have a look

movable pulley summary

when in use A pulley whose axis moves with an object is called a movable pulley. The movable pulley can be regarded as a labor-saving lever, O is the fulcrum of the lever, and the axis of the pulley is the action point of resistance. The force of the lifted object on the shaft is resistance, and the force of the rope on the wheel is power. When lifting heavy objects, if the ropes on both sides are parallel, the power arm is twice the resistance arm; When the movable pulley is balanced, the power is half of the resistance

the function and characteristics of the movable pulley

1. Understand the function of the movable pulley when the force acts on the wheel and shaft: it can save labor, but cannot change the direction of the force

2, the movement of the movable pulley can save labor. The movable pulley is a labor-saving lever

3, using the movable pulley can save half the effort and distance. This is because when using the movable pulley, the hook code is hung by two ropes, and each rope only bears the movable pulley with the weight of the hook code. Although the use of the movable pulley saves force, the distance of the dynamic movement is twice the distance of the hook code, that is, it costs distance. The direction of the force cannot be changed. Move as an object moves

4, the pulley whose position of the shaft moves with the pulled object is called the moving pulley

5, if the weight is directly hung on the pulley, the pulley also rises when lifting the weight. Such a pulley calls the pulley

6, if a person stands on the object being pulled to pull the rope, the pulley moving relative to the ground is equivalent to the fixed pulley, and the fixed pulley is the movable pulley. Therefore, the definition of the movable pulley is that relative to the person applying the force, if the pulley moves, it is the movable pulley, otherwise it is the fixed pulley. The weight of the movable pulley is halved

7, regardless of the gravity on the moving pulley itself, using the moving pulley can save half the force, but at this time, the direction of force cannot be changed. Pull the rope upward to lift the weight

labor saving calculation

first, f=g/2 (idealized, excluding the weight of the pulley and only one movable pulley)

second, f= (g+g movable pulley)/2 (considering the weight of the movable pulley and only one movable pulley)

third, f= (g+g movable pulley)/n (n represents the number of segments of the rope connected to the movable pulley, which is a pulley block)

the above is the introduction that Xiaobian brings to you. For more relevant knowledge, please continue to pay attention to Qijia consultation, Please look forward to more wonderful inquiries

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