Question 1: What are the benefits of using a pulley?
The pulley consists of a grooved disk that can rotate around a central axis and a flexible cable (rope, tape, steel cable) that spans the disk , chains, etc.) that can rotate around a central axis. The pulley is a deformation of the lever and belongs to the simple lever type machine. In our country, there are records about pulleys in the book "Mo Jing" as early as the Warring States Period. The pulley with a fixed central axis is called a fixed pulley. It is a deformed equal-arm lever that does not save effort but can change the direction of the force. The pulley whose central axis moves together with the weight is called a movable pulley. It is a deformed unequal arm lever that can save half the force but does not change the direction of the force. In practice, a certain number of movable pulleys and fixed pulleys are often combined into various forms of pulley blocks. The pulley block saves effort and can change the direction of force.
The differential pulley (commonly known as a hand chain hoist) commonly used in factories is also a pulley block. Pulley blocks are widely used in cranes, hoists, lifts and other machinery.
There are two types of pulleys: fixed pulleys and movable pulleys
(1) Fixed pulleys are essentially equal-arm levers, which are effortless and effortless, but can change the direction of the force.
Characteristics of the fixed pulley
It is not labor-saving to use the fixed pulley to pull the hook code. The reading of the spring balance is the same with or without the fixed pulley. It can be seen that using a fixed pulley does not save effort but can change the direction of the force. In many cases, changing the direction of the force will bring convenience to the work.
The principle of the fixed pulley
The fixed pulley is essentially an equal-arm lever. The power L1 and resistance L2 arms are equal to the radius of the pulley. According to the lever balance condition, it can also be concluded that the fixed pulley is not labor-saving.
(2) The movable pulley is essentially a lever with twice the power arm as the resistance arm, saving 1/2 the effort and spending 1 times the distance.
Characteristics of the movable pulley
Using a movable pulley can save half the effort and waste distance. This is because when using a movable pulley, the hook code is hung by two sections of rope, and each section of rope only bears half of the weight of the hook code. Although using the movable pulley saves effort, the distance moved by the power is greater than the distance the hook code is raised, that is, the distance is wasted.
The principle of the movable pulley
The movable pulley is essentially a lever whose power arm (L1) is twice the resistance arm (L2).
(3) Pulley block: A pulley block composed of a fixed pulley and a movable pulley, which saves labor and can change the direction of the force.
The pulley block uses several lengths of rope to hang the object and lift the object. The force is a fraction of the total weight. The free end of the rope that goes around the movable pulley is counted as a section, but the one that goes around the fixed pulley is not counted.
Although using a pulley block saves effort, it costs a lot of distance. , the distance moved by the power is greater than the distance moved by the heavy object.
Purpose of the pulley block:
In order to save money and change the direction of the power, the fixed pulley and the movable pulley can be combined into a pulley block.
Effort-saving
When using a pulley block, the pulley block uses several lengths of rope to hang the object, and the force used to lift the object is only a fraction of the weight of the object.
Characteristics of the pulley block
Using the pulley block to do experiments, it is easy to see that although using the pulley block saves effort, it costs distance - the distance moved by power is greater than the distance the goods are lifted. .
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, steel cable, chain, etc.) that spans the disc. . The pulley is a deformation of the lever and belongs to the simple lever type machine. In our country, there are records about pulleys in the book "Mo Jing" as early as the Warring States Period. The pulley with a fixed central axis is called a fixed pulley. It is a deformed equal-arm lever that does not save effort but can change the direction of the force. The pulley whose central axis moves together with the weight is called a movable pulley. It is a deformed unequal arm lever that can save half the force but does not change the direction of the force. In practice, a certain number of movable pulleys and fixed pulleys are often combined into various forms of pulley blocks. The pulley block saves effort and can change the direction of force.
The differential pulley (commonly known as a hand chain hoist) commonly used in factories is also a pulley block. Pulley blocks are widely used in cranes, hoists, lifts and other machinery.
There are two types of pulleys: fixed pulleys and movable pulleys
(1) Fixed pulleys are essentially equal-arm levers, which are effortless and effortless, but can change the direction of the force.
Characteristics of the fixed pulley
It is not labor-saving to use the fixed pulley to pull the hook code. The reading of the spring balance is the same with or without the fixed pulley. It can be seen that using a fixed pulley does not save effort but can change the direction of the force. In many cases, changing the direction of the force will bring convenience to the work.
The principle of the fixed pulley
The fixed pulley is essentially an equal-arm lever. The power L1 and resistance L2 arms are equal to the radius of the pulley. According to the lever balance condition, it can also be concluded that the fixed pulley is not labor-saving.
(2) The moving pulley is essentially a power arm acting as a resistance... >>
Question 2: What are the benefits of pulley sliding 1. Adjusting the amount of exercise can achieve various effects, such as weight loss and so on.
- Burning 570 to 1150 calories per hour is as effective as running
- Generally speaking, the maximum oxygen consumption of roller skating (the benchmark for measuring exercise intensity) is running 90%, which is very effective in maintaining the optimal intensity of aerobic exercise.
- According to research, the heartbeat measured while maintaining a speed of 23km/hr roller skating is 74% of the maximum heartbeat. This is a typical aerobic exercise that can achieve the effects of strengthening cardiovascular and burning fat.
- Accelerate the speed to 28km/hr, and the heart rate will reach 85% of the highest heart rate and exceed the anaerobic threshold. At this time, the endurance of the muscles can be improved.
- By continuously roller skating, you can adjust your body to the best condition.
2. Low risk of injury
- Because roller skating is different from running, the wheels rotate when the roller skating is stepped on. The elasticity of the wheels made of polyurethane has little impact on the joints, so the elderly are also suitable for this activity. Sports - Wear a helmet and protective gear, the risk of injury after falling is very small
3. It is a very good exercise for children in the growing period
- Improves the sense of balance, movement, physical strength, endurance, etc. to help the growth and development of children during the growing period
- In Exercising outdoors with more people can make your personality more cheerful
- It has the effect of burning fat and can prevent the symptoms of obesity in children
4. Exercises to do with the family
- From growing children to the elderly, men, women and children can enjoy exercise together
- Exercises that are easy to learn
- It is also easy for women to learn. In fact, the male to female ratio of roller skaters is 50:50
5. Economical sports
- If you buy good equipment when you are a beginner, you will almost never have to spend anything else
- Unlike swimming, tennis and other sports, roller skating does not require a specific place and does not cost as much as entering. Money from field tickets
- can be used as a means of transportation according to your own strength
6. You can make more friends through roller skating
- Contact more people by participating in clubs and other activities and you will make many friends
- You can roller skate alone, and it is more beneficial to roller skate with multiple people Interest
7. It’s not easy to get bored
- Roller skating can be used in various sports such as leisure, speed skating, street racing, freestyle, roller skating, and tricks, so it’s not easy to get bored
- Look at yourself You will feel a sense of accomplishment with the development of roller skating technology
8. When reaching a certain technical level, extra points will be added in the college entrance examination
- Candidates who have won the title of national second-level athlete or above and have been tested and recognized by the provincial admissions committee in the year of application. The score can be added appropriately based on the total score of the candidates' unified examination scores
Question 3: What is the difference between wheels and pulleys in life? Wheels are used to put cars underground. Rolling friction replaces sliding friction, which is more labor-saving. Pulleys are used to lift goods, and are divided into movable pulleys and fixed pulleys. Fixed pulleys are used to change the stretching direction of the rope and do not have a labor-saving effect. The movable pulleys do not have the role of changing the stretching direction of the rope, but saving half the force.
Question 4: What are the skills for roller skating? Roller skates are divided into single row and double row. For single row skates, you should pay attention to the fact that when sliding, it looks like a figure of eight when viewed from the front. Just stand up and push outwards. .
The double-row ones are different. It seems that the double-row ones are easier to stand than the single-row ones. In fact, that is not the case. The double-row ones use one foot as the axis and the other foot to push hard. Can be exchanged to change direction!
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Roller skating skills
Jumping (high jump and long jump)
Before jumping, bend your knees and lower your center of gravity. When you jump, straighten your knees instantly and move your body forward. Pull up, wait until your feet leave the ground, and lift your knees as high as possible, as close to your chest as possible. When falling, land with your feet apart in front of one another, and your center of gravity will be more stable!
Going down the stairs:
Sliding down the stairs from the front and sliding down the stairs from the back. Don’t think it is a staircase. You must slide it as if it were flat ground. Spread your feet forward and backward, with the center of gravity between the two feet! If you slide forward, usually the third or fourth wheel will hit the stairs, the center of gravity should be placed on the heels, but between the two feet, remember to squat low and the feet should be open front and back!! < /p>
Beginners should start from step 1.2. The wider the step, the better (it should not be too exaggerated). Practice going up at 30, 45, 60, and 75 degrees. Be careful to go faster, otherwise you will get stuck.
a) Sliding forward: First, accelerate to an appropriate speed. When approaching the stairs, kneel in a high position, keep your body straight, do not lean forward or backward, and slide down.
Squat your knees slightly, spread your feet forward and backward, about toes to heels, and then tilt down at an angle of about 45 degrees. Maintain a certain speed, relax your knees, and keep a certain distance between your feet. Start with the first step, then the second step, and the third step. , fourth level, if you have the opportunity, correct the angle again, 60 degrees... 75 degrees. If you are not sure, don't try 90 degrees easily. Pay attention to the softness of your knees to avoid sports injuries. Beginners must wear protective gear..
b) Back sliding: Practice the back sliding first. Generally speaking, the back sliding is more stable than the front sliding. Remember to wear protective gear. Accelerate to the appropriate speed, and when approaching the stairs, switch to sliding backwards, with your feet in a lunge one after another, and slide down. The focus is on the back foot. The most important thing is to overcome the fear. The key is to support the feet and not to jump. The posture of the feet on the stairs will be deformed. The feet must be stable. No matter what happens, the feet cannot be combined. Do not move forward or backward.
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1. Standing
1) T-shaped standing method: Place your left heel against the inside of your right foot, stand in a T shape, and lean your upper body slightly forward.
2 ) Parallel standing method: Stand with your feet parallel and shoulder width apart, and lean your upper body slightly forward.
Note: Do not adduct or abduct the corners during standing, keep the knife holder vertical to the ground, and pay attention to developing a good standing posture during daily exercise
3) Squat Posture: The upper body leans forward, the shoulders and back are slightly higher than the hips, the hands hold each other or swing naturally, the legs are bent, the upper body and the ground are at an angle of 15-20 degrees, the knee joints are at an angle of 90-110 degrees, and the ankle joints are at an angle of 50-50 degrees. 70 degree angle.
Pay attention to the squatting exercises to experience each movement during the exercise.
2. Exercises to move the center of gravity
1) Stand and step on the spot
Wear your roller skates, stand with your feet parallel and shoulder width apart, and your legs slightly apart. Bend, lean your upper body slightly forward, and let your arms droop naturally. Move your center of gravity to your left leg, lift your right leg slightly and then lower it; move your center of gravity to your right leg, lift your left leg slightly and then lower it. Repeat this and gradually speed up.
2) One-leg support for balance
On the basis of mastering the standing position, maintain the original posture, hold the railing or a companion, and shift the center of gravity to one leg and the other leg Extend to the side and return to the starting position, then change feet and repeat the above action.
3) "Eight" walking practice
Stand with your feet in an eight-figure shape, shift the center of gravity to the left foot, take a step forward with the right foot, and then move the center of gravity to the right foot then lift your left foot and take a step forward, then move the center of gravity to the left leg, then lift the right foot and take a step forward, move the center of gravity to the right leg, and so on
3) Cross walking
Standing in place, first shift the center of gravity to the left leg, retract the right leg, step towards the front and outside of the left leg into a cross posture, then move the center of gravity to the right leg, then retract the left leg of the left leg and take one step to the left. Start the pose and practice it over and over again; also practice taking steps toward the body.
3. Sliding on a straight track
1) Push on the ground with one foot and slide with both feet to practice
Push the inside edge of your right foot on the ground and push your center of gravity to the front of your body while gliding forward. On the left leg, push the right foot on the ground and quickly bring it together with the left foot to slide forward. Then push the left foot on the ground and bring them together, and practice gliding forward alternately and repeatedly.
2) Sliding with one foot on the ground
Lean your upper body forward, let your arms droop naturally, stand with your feet slightly apart, and stand in a splayed shape, heavy... >>
Question 5: What are the benefits of playing on a pulley? I have been playing for several years. I don’t think it has much benefit, but it is quite fun to play in your spare time. Playing roller skating when you are in a bad mood can also make you happy. I personally think Pulley sports is a relatively exciting sport. It is challenging. I am happy to be your friend!
Question 6: What is the difference between axle, bearing and pulley? The axle has a central rotating shaft in the middle. round wheel.
A bearing is an object that is inserted into an object with a hole in the middle and can rotate freely.
There are two types of pulleys: dynamic pulleys and static pulleys, that is: the overall system in which a rope passes over a round wheel is called a pulley.