The relationship between the mechanical efficiency of the movable pulley and the direction of the pu

Gravitational potential energy. The increased efficiency will be reduced.

The =w you give has w total =gh fs=g 2f only counts the gravitational potential energy, not the kinetic energy.

Mechanical efficiency. =(w total -e within) w total, that's right.

If not pull the free end of the rope vertically,"

In other words, the direction of the human pull force and the pull direction of the top of the wall are both oblique, and not only the size of the pull force will increase.

Moreover, when the object rises to the height of h, the distance of the rope will be greater than 2h, so when g and h are unchanged, f and s are expanded, and the efficiency of potential energy improvement will decrease.

Reference calculations. Let , the angle between f and the horizontal direction be

f=g/2sinα

s=2h/sinα

0≤sinα≤1)

In addition, the object should be moved vertically upwards

In the process, the angle becomes smaller, f increases, and the increase in s relative to the height increases.

Mechanical energy efficiency becomes larger.

Let , the dynamic friction factor is

E within = GS (where G is the total gravity of the pulley and the weight) = (W total - E inside) W Total.

f-μg)/f

1-μg/f

g is a fixed value, f becomes larger, becomes larger.

The movable pulley can not change the direction, if it is not pulled in the vertical direction of the free end of the rope, it can be seen that the pulling force is greater at this time. The increase in tensile force is due to the increase in friction force and the mechanical efficiency =g (g+g +f) 100 at this point decreases in mechanical efficiency.

I really wanted to know the answer, and I waited quietly.

I think this sentence is correct under certain conditions of orange pie. Strict definition: the mechanical efficiency of the pulley block = the weight multiplied by the rising height The weight of the weight multiplied by the rising height + the rope mass multiplied by the rising height (generally negligible) + the frictional work done (generally negligible) + the total mass of the movable pulley multiplied by the rising height, in most cases, some items that can be ignored can be removed such as the influence of friction and the rope itself, the mechanical efficiency of the pulley block = the weight multiplied by the rising height The weight of the weight multiplied by the rising height + the total mass of the movable pulley multiplied by the rising height, simplify the formula again, the mechanical efficiency of the pulley block = 1 (1+The total weight of the movable pulley is the mass of the weight), observing this formula, the effect of mechanical efficiency is the ratio of the total weight of the movable pulley to the amount of heavy material (the total weight of the movable pulley and the mass of the weight).

If you compare different pulley sets, the work done by the pull force of the pulley block with high mechanical efficiency is not necessarily large, because the influence of mechanical efficiency is the ratio of the total weight of the movable pulley to the amount of heavy material (the mass of the total weight of the movable pulley).

If you compare the same pulley group, it is true that the greater the mechanical efficiency, the greater the work done by the pulling force, and the influence of rope weight and friction can generally be ignored (unless the weight lifted is very light, the influence of friction force will be relatively large, and this sentence is not valid under this condition).

A pulley block is a commonly used mechanical device that manufactures power by lifting heavy objects at a constant speed. In this case, there is a certain relationship between the mechanical efficiency of the pulley block and the power of the pulling force.

Mechanical efficiency is the percentage of mechanical kinetic energy that can be converted into mechanical kinetic energy by the power used to lift a heavy load in a pulley block. If the mechanical efficiency is very high, it means that the pulley block can effectively use the infiltration search force, so as to generate a large amount of mechanical kinetic energy.

Therefore, there is a certain relationship between the mechanical efficiency of the pulley block and the power of the pulling force, and when the mechanical efficiency is improved, the power of the pulling force can also be increased accordingly. Conversely, if the mechanical efficiency decreases, the power of the pulling force also decreases.

The mechanical efficiency of the movable pulley is obtained by the formula =w has w total 100%.

The pulley in which the position of the shaft moves with the object being pulled is called a movable pulley. The movable pulley is essentially a lever (labor-saving lever) in which the power arm is equal to 2 times the resistance arm. It cannot change the direction of the force, but it can save up to half of the force, but it does not save work.

It can form a pulley group with a fixed pulley. It is a simple machine commonly used in daily life.

Mechanical efficiency refers to the percentage of the output work (useful work) and the input work (power work) of the machinery when the machine is running stably. The main contents include pulley block, inclined plane efficiency, lever rotation, common efficiency, and increased efficiency. The mechanical efficiency of the pulley block is the weight of the body, followed by the weight of the pulley, the weight of the rope and the friction.

Whether you use the same pulley to lift an embroidery needle or a weight far greater than the moving pulley, you need to lift the movable pulley, but also to overcome the rope weight and friction, the former extra work is far greater than the useful work, its mechanical efficiency is almost zero, the latter extra work in the total work accounted for in the ratio is so small that the cavity is more, so the greater the weight, the higher the mechanical efficiency.

The historical origin of pulleys:

The earliest painting of the pulley appears in an Assyrian relief in the eighth century BC. This relief shows a very simple pulley that can only change the direction of force, and the main purpose is to facilitate the application of force in order to facilitate the application of force, and does not give any mechanical benefit. In China, the drawing of pulley devices first appeared in the Han Dynasty portrait bricks, pottery well molds and Wu Qing.

There is also a record of the discussion of pulleys in the Book of Ink.

The ancient Greeks classified pulleys as simple machinery. As early as 400 BC, the ancient Greeks already knew how to use a compound pulley. Around 330 B.C., Aristotle's eighteenth problem in his book "Mechanical Problems" was devoted to the "compound pulley" system.

Archimedes contributed a lot of knowledge about simple mechanics and explained in detail the kinematic theory of pulleys. Archimedes is said to have used a duplex pulley alone to pull a large ship full of cargo and passengers.

In the first century, Alessandro analyzed and wrote the theory of compound pulleys, proving that the ratio of load to force is equal to the number of rope segments that bear the load, known as the "pulley principle".

Summary. Dear, I'm glad to answer for you...When cable-pulled, the useful work and extra work do not change, and the mechanical efficiency must remain the same. Some people think that the pull force has become larger, but they do not think that the distance that the rope has pulled has become smaller.

Dear, I'm glad to answer for you...When the cable-stayed pull, the useful work and extra power have not changed, and the mechanical effect of the town will definitely remain the same. Some people think that the force of pulling the back to the shed has become larger, but they do not expect that the distance that the rope has pulled has become smaller.

The answer we give is to get smaller.

Suihua Middle School Exam Questions.

Getting smaller is right for a pro.

Didn't you say unchanged?

The mechanical efficiency remains the same.

I'm sorry to be wrong.

The question is about mechanical efficiency.

The answer is on the small side.

That's a mistake, pro, the mechanical efficiency remains the same.

Yes, the pro-mechanical efficiency remains the same.

If you ignore the pulley weight and friction, then.

1. For movable pulleys, the tensile force at the end of the rope is half of the weight of the weight of the heavy object;

2. For the fixed spike opening wheel, the tension at the end of the rope is equal to the weight of the heavy object.