Question 2: What are the benefits of roller skating? 1. Adjusting the amount of exercise can get various exercise effects, such as losing weight.
-Burning 570 to 1 150 calories per hour is as good as running.
Generally speaking, the maximum oxygen consumption of roller skating (the benchmark for measuring exercise intensity) is 90% of that of running, which is very effective for maintaining the optimal intensity of aerobic exercise.
According to research, the heartbeat measured when skating at a speed of 23km/h is 74% of the maximum heartbeat. It is a typical aerobic exercise, which can strengthen the cardiovascular system and burn fat.
-When the speed is increased to 28km/hr, the heart rate will reach 85% of the highest heart rate and exceed the anaerobic threshold, which can improve muscle endurance.
You can adjust your body to the best condition by skating constantly.
2. The risk of injury is very small.
-Because roller skating is different from running, it will cause the wheels to turn when stepping, and the elasticity of the wheels made of polyurethane has little influence on the joints, so the elderly are also suitable for this sport. -Wear a helmet and protective gear, and there is little risk of injury after falling.
This is a very good exercise for growing children.
-Improve the sense of balance, exercise, physical strength and endurance, and help children grow and develop during their growth.
-Do more outdoor sports with others to make yourself cheerful.
-The effect of burning fat can prevent the symptoms of childhood obesity.
4. Exercise with your family
-From growing children to the elderly, men, women and children can enjoy sports together.
-Easy to learn exercise
Women are easy to learn. In fact, the ratio of male and female skaters is 50: 50.
5. Economic sports
-If you buy good equipment when you are a beginner, you hardly need to spend any other money.
-Unlike swimming, tennis and other sports, roller skating doesn't need a specific place, and it doesn't cost money like tickets.
-you can use it as a means of transportation according to your own strength.
You can make more friends by roller skating.
-Get to know more people and make many friends by participating in clubs and other activities.
-You can skate alone, and more people are interested in skating together.
7. It's not easy to get bored
-Roller skating can do leisure, speed skating, street brushing, flat flower, roller skating, pattern and other diversified sports, and will not get tired easily.
Look at the development of your roller skating skills, and you will have a great sense of accomplishment.
When you reach a certain technical level, you will get extra points in the college entrance examination.
-candidates who won the title of national second-class athlete or above in the same year and were tested and approved by the provincial admissions Committee. On the basis of the total score of candidates' unified examination results, the score can be appropriately improved.
Question 3: What are the advantages of using pulleys?
A simple machine that can rotate around the central axis consists of a grooved disc that can rotate around the central axis and a flexible cable (rope, adhesive tape, steel cable, chain, etc.). ) across the disk. Pulley is the deformation of lever, which belongs to lever simple machinery. In China, as early as the Warring States Period, there was a record about pulleys in the book Mo Jing. The pulley with the fixed central shaft is called the crown block, which is a deformed equal arm lever, and can change the direction of force without any effort. The pulley whose central axis moves with the weight is called the movable pulley, which is a deformed unequal arm lever, and can save half the force without changing the direction of the force. In practice, a certain number of moving pulleys and crown block are often combined into various pulley blocks. The pulley block can save labor and change the direction of force.
The differential pulley (commonly known as chain block) commonly used in factories is also a kind of pulley block. Pulley blocks are widely used in cranes, winches, elevators and other machinery.
There are two kinds of pulleys: crown block and moving pulley.
(1) The crown block is essentially an equal arm lever, which is labor-saving and effortless, but it can change the direction of the acting force.
Characteristics of crown block
It is not labor-saving to pull the hook code through the crown block. Whether there is a crown block or not, the reading of the spring scale is the same. It can be seen that the direction of force can be changed easily by using the crown block. Many times, changing the direction of force will bring convenience to work.
Crown block principle
The crown block is essentially an equal arm lever, and the power L 1 and the resistance L2 arm are equal to the pulley radius. According to the lever balance condition, it can also be concluded that the crown block is not labor-saving.
(2) The moving pulley is essentially a lever with twice the power arm as the resistance arm, which saves the force of 1/2 and spends the distance of 1 times more.
Characteristics of moving pulley
Using a moving pulley can save half the force and waste the distance. This is because when using the moving pulley, the hook code is hung by two ropes, and each rope only bears half the weight of the hook code. Although the use of moving pulley saves power, the distance of power moving is greater than the distance of hook code rising, that is, the distance is wasted.
Moving pulley principle
The moving pulley is essentially a lever, and its arm of force (L 1) is twice as big as the arm of resistance (L2).
(3) Pulley block: A pulley block consisting of a crown block following pulleys, which can save labor and change the direction of force.
The pulley block uses several lengths of rope to lift the object, and the force used to lift the object is a fraction of the total weight. The free end of the rope bypasses the moving pulley, but it is not.
Although using pulley block saves labor, it consumes distance, and the distance of power movement is greater than that of heavy objects.
Purpose of pulley block:
In order to save energy and change the direction of power, the crown block and the moving pulley can be combined into a pulley block.
Labor-saving size
When using the pulley block, the pulley block uses several pieces of rope to lift the object, and the force used to lift the object is a fraction of the weight of the object.
Characteristics of pulley block
It is easy to see that the pulley block is labor-saving, but it consumes distance-the distance of power moving is greater than the distance of goods rising.
A simple machine that can rotate around the central axis consists of a grooved disc that can rotate around the central axis and a flexible cable (rope, adhesive tape, steel cable, chain, etc.). ) across the disk. Pulley is the deformation of lever, which belongs to lever simple machinery. In China, as early as the Warring States Period, there was a record about pulleys in the book Mo Jing. The pulley with the fixed central shaft is called the crown block, which is a deformed equal arm lever, and can change the direction of force without any effort. The pulley whose central axis moves with the weight is called the movable pulley, which is a deformed unequal arm lever, and can save half the force without changing the direction of the force. In practice, a certain number of moving pulleys and crown block are often combined into various pulley blocks. The pulley block can save labor and change the direction of force.
The differential pulley (commonly known as chain block) commonly used in factories is also a kind of pulley block. Pulley blocks are widely used in cranes, winches, elevators and other machinery.
There are two kinds of pulleys: crown block and moving pulley.
(1) The crown block is essentially an equal arm lever, which is labor-saving and effortless, but it can change the direction of the acting force.
Characteristics of crown block
It is not labor-saving to pull the hook code through the crown block. Whether there is a crown block or not, the reading of the spring scale is the same. It can be seen that the direction of force can be changed easily by using the crown block. Many times, changing the direction of force will bring convenience to work.
Crown block principle
The crown block is essentially an equal arm lever, and the power L 1 and the resistance L2 arm are equal to the pulley radius. According to the lever balance condition, it can also be concluded that the crown block is not labor-saving.
(2) The essence of moving pulley is power arm is resistance ... >; & gt
Question 4: What kinds of roller skating events are there? Types of roller skating events in Migao Midland
1, flat fancy freestyle gyration
By combining roller skates with traditional double-row wheels and hip-hop movements, fancy winding is gathered.
Pile, obstacle speed, stop, jump, block, wheel dance, etc. Make it more fun to play inline skating.
2. Artistic skating in figure skating
Roller skating events similar to figure skating include four basic competitions: compulsory figure skating, free skating, pair skating and dancing.
3. Speed skating speed
It is a kind of roller skating competition similar to speed skating, which is divided into track race, road race and marathon.
4. Roller hockey
This is a fierce competition in roller skating. Players wear double-row wheels or single-row wheels and hold sticks to play the game. There are four players and a goalkeeper on each side of the game.
5, extreme roller skating X-Game
It is one of the most exciting sports at present and is very popular with young friends. Take musical instruments as the main activity background, such as U-way.
I hope this helps.
Question 5: What are the formulas for pulleys? The crown block can change the direction of force within 30 minutes, but it can't save energy. Moving the pulley can save half the force, but it cannot change the direction of the force.
Question 6: What are the specifications of wire rope pulleys? According to the design of wire rope diameter, it is generally 40-60 times the diameter of wire rope. If the wire rope diameter is 10 mm, the corresponding wire rope pulley diameter is 400-600 mm, which is for reference only.
Commonly used steel wire ropes include phosphating coated steel wire rope, galvanized steel wire rope, stainless steel wire rope or plastic coated steel wire rope, which are used in atmospheric environment. Manganese phosphating coated steel wire rope produced by patented technology has the longest service life, and hot dip galvanized-phosphating double coated steel wire rope is preferred in heavy corrosive environment. Phosphating coating improves the wear resistance and corrosion resistance of wire rope, which is the reason for improving the service life of wire rope, and smooth wire rope is being completely eliminated.
Phosphating coated steel wire rope, manganese series or zinc-manganese series phosphating is preferred. Compared with the production process of smooth steel wire rope, only the wear-resistant phosphating process before rope making is added, and the wear resistance and corrosion resistance of steel wire are greatly improved. Phosphating steel wire is directly twisted into steel wire rope without cold drawing. At present, the fatigue test data show that the fatigue life of phosphating coated steel wire rope is about three times that of smooth steel wire rope with the same structure (under comparable conditions in the laboratory), and the reason for the great extension of the service life of steel wire rope is that it is not easy to wear and rust, which has far exceeded that of imported steel wire rope. Manganese phosphating film can solve the wear problem of steel wire rope in use and improve corrosion resistance, which is for reference only.
Question 7: How many kinds of roller skating are popular in the world at present? There are roughly the following types:
Fitness, aggression, hockey, free skating, speed, Slalomn, sliding, downhill, jumping, stepping, catching, traction, art, basket, dance, cross-country
1. Fitness. Generally, it refers to brushing the street, which is the most popular form of leisure roller skating. Some aging urbanites abroad regard roller skating as a way of fitness, just like running, or a means of transportation. So there is no technical requirement for it, as long as it can slide forward, stop and turn. In addition, the outdoor roller skating activity from one city to another is different from speed skating, its speed is in the middle, and the brushing distance is generally less than 40KM.
2. Aggressive. Generally refers to extreme roller skating, which is a special form of roller skating. These include "street" and "ramp" (U-shaped pool), and everyone interprets their understanding of "limit" through various means.
3. Hockey. What we are talking about now is roller hockey. The main types of hockey are roller hockey, inline hockey, street hockey and ring hockey. Each kind of hockey has its own differences in details, such as court, ball, club and knife.
4. Freestyle skating. This is what people often say. FSK, freestyle roller skating can be translated as "freestyle roller skating". This is a very new roller skating event, which was invented in Europe only two or three years ago. Its main inspiration comes from the speed and aggressive skills of fitness, combined with downhill, speed skating and acrobatic roller skating, which is a brand-new way to reflect the development of modern roller skating and has become a symbol of roller skating spirit in European and American cities.
5. Speed. Generally refers to speed roller skating, including track and short track races. The difference from other roller skating is mainly in speed and professional configuration.
6. Obstacle skiing. This refers to flat flowers, mainly including freestyle skirts and speed skirts. At present, the popular flat skates are mainly single-row skates. In some European cities, quads are also used to play flat skates. The wheels of this kind of flat Hua Shuang roller skates are generally as soft as 78A, which is quite different from the double-brand roller skates that we often practice figure skating on the indoor wooden floor, mainly because one wheel is suitable for indoor use and the other wheel is suitable for outdoor use.
7. Slide. This refers to the braking technology, sometimes called Cess Slide, which is designed to stop in a short time under different circumstances. Personally, I think its content, style and difficulty coefficient are very different from Slalomn, so it is called a class alone. Among them, the well-known technical movements are: power sliding, parallel sliding, magic, acid and so on.
8. Downhill. This refers to downhill. As we know from the name, it should be a process of rapidly sliding from a high mountain to the end of the mountain. Its risk coefficient and difficulty coefficient, even for a more skilled speed skater, is also a challenge. The speed of rushing down the mountain can often reach 70 kph-80 kph, which is unbearable for untrained players. As far as its equipment is concerned, speed equipment is generally used, and it is necessary to bring a helmet and a full set of protective gear during the game. In addition, in some European countries, such as France, it is forbidden to play downhill on public roads, mainly for safety reasons.
9. Jump. This refers to jump, which includes: style jump or pattern jump, acrobatic jump or pure height jump, high platform jump ... >; & gt
Question 8: How many kinds of sliding door pulleys are there? There are two kinds of common pulleys in the market: ordinary pulleys and buffer pulleys. Wrigley wardrobes are basically resistant.
Buffer pulley, small impact, low noise and long service life.