Preview:
School p.Third decisive
Report
discipline: "Physics"
on the topic:" "
Completed:
student_7___ class
Tolokonnikova Vladimir
Checked by: Oleinikov Nikolai
Viktorovich
__________________________
Levers in nature, everyday life and technology
The lever is one of the most common and simple types of mechanisms in the world, present both in nature and in the man-made world.
The human body as a lever
For example, the skeleton and musculoskeletal system of a person or any animal consists of tens and hundreds of levers. Let's take a look at the elbow joint. The radius and humerus are connected together by cartilage, and the muscles of the biceps and triceps are also attached to them. So we get the simplest lever mechanisms.
If you hold a 3 kg dumbbell in your hand, how much effort does your muscle develop? The junction of the bone and muscle divides the bone in a ratio of 1 to 8, therefore, the muscle develops a force of 24 kg! It turns out that we are stronger than ourselves. But the lever system of our skeleton does not allow us to fully use our strength.
A good example of the better application of leverage to the musculoskeletal system is the reverse hind knee in many animals (all kinds of cats, horses, etc.).
Their bones are longer than ours, and the special structure of their hind legs allows them to use the strength of their muscles much more efficiently. Yes, of course, their muscles are much stronger than ours, but their weight is an order of magnitude greater.
The average horse weighs about 450 kg, and at the same time can easily jump to a height of about two meters. To perform such a jump, you and I need to be masters of sports in high jumps, although we weigh 8-9 times less than a horse.
Since we remembered the high jump, consider the options for using the lever, which were invented by man. Pole high jumpvery clear example.
With the help of a lever about three meters long (the length of the pole for high jumps is about five meters, therefore, the long arm of the lever, starting at the bend of the pole at the time of the jump, is about three meters) and the correct application of effort, the athlete takes off to a dizzying height of up to six meters.
Lever in everyday life
Levers are also common in everyday life. It would be much more difficult for you to open a tightly screwed faucet if it did not have a 3-5 cm handle, which is a small but very effective lever.
The same applies to a wrench, which you use to unscrew or tighten a bolt or nut. The longer the wrench, the easier it will be for you to unscrew this nut, or vice versa, the tighter you can tighten it.
When working with especially large and heavy bolts and nuts, for example, when repairing various mechanisms, cars, machine tools, wrenches with a handle up to a meter are used.
Another striking example of leverage in Everyday life most common door. Try to open the door by pushing it near the hinges. The door will give in very hard. But the farther from the door hinges the point of application of force is located, the easier it will be for you to open the door.
Levers in technology
Naturally, levers are also ubiquitous in technology.The most obvious examplegear shift lever in a car. The short lever arm is the part that you see in the cabin.
The long arm of the lever is hidden under the bottom of the car, and is about twice as long as the short one. When you shift the lever from one position to another, a long arm in the gearbox switches the corresponding mechanisms.
Here you can also very clearly see how the length of the lever arm, the range of its travel and the force required to shift it correlate with each other.
For example, in sports cars, for faster gear changes, the lever is usually set short, and its range is also made short.
However, in this case, the driver needs to make more effort to change gear. On the contrary, in heavy vehicles, where the mechanisms themselves are heavier, the lever is made longer, and its range of travel is also longer than in a passenger car.
Thus, we can be convinced that the mechanism of the lever is very widespread both in nature and in our everyday life, and in various mechanisms.
Since ancient times, simple mechanisms have often been used in complex, in a variety of combinations.
The combined mechanism consists of two or more simple ones. This is not necessarily a complex device; many fairly simple mechanisms can also be considered combined.
There are many types of simple mechanisms. This is a lever, and a block, and a wedge, and an inclined plane, and many others.
In physics, simple mechanisms are called devices that serve to transform forces.
The use of simple mechanisms is very common both in production and in everyday life.
For example, in a meat grinder there is a gate (handle), a screw (pushing meat) and a wedge (knife-cutter).
An inclined plane that helps roll in or pull heavy objects up is also a simple mechanism.
Wrist watch hands are rotated by a system of gears of different diameters, meshing with each other. One of the most famous simple combined mechanisms is a jack. The jack is a combination of screw and collar.
Most often, simple mechanisms are used in order to obtain a gain in strength, that is, to increase several times the force acting on the body.
A lever in physics is a simple mechanism
In physics, a lever is a rigid body that can rotate around a fixed support.
A crowbar, a board, and the like can be used as a lever.
There are two types of levers. For a lever of the first kind, the fulcrum O is located between the lines of action of the applied forces. At the lever of the second kind, the fulcrum is located on one side of them. That is, if we are trying to move a heavy object with a crowbar, then a lever of the first kind is a situation when we put a bar under the crowbar, pressing down on the free end of the crowbar. An immovable support in our this case will be a bar, and the applied forces are located on both sides of it. And the lever of the second kind is when we, having slipped the edge of the crowbar under the weight, pull the crowbar up, thus trying to turn the object over. Here, the fulcrum O is located at the point where the crowbar rests on the ground, and the applied forces are located on one side of the fulcrum.
Using leverage allows you to get a gain in strength. So, for example, the worker shown in the left figure, applying a force of 400 N to the lever, will be able to lift a load weighing 800 N. Dividing 800 N by 400 N, we get a gain in force equal to 2.
The law of balance of forces on the lever
Using the lever, we can gain strength and lift a heavy load with our bare hands. The distance from the fulcrum to the point of application of the force is called the shoulder of the force. Moreover, the balance of forces on the lever can be calculated using the following formula:
F 1 / F 2 \u003d l 2 / l 1,
where F 1, F 2 - forces acting on the lever,
and l 2 , l 1 are the shoulders of these forces. (In the figure above, OB and OA are lever arms)
This law was established by Archimedes in the third century BC. It follows from this that a smaller force can balance a larger one. To do this, it is necessary that the shoulder of the smaller force be greater than the shoulder of the greater force. And the gain in strength obtained with the help of a lever is determined by the ratio of the shoulders of the applied forces.
Nowadays, levers are widely used both in production (for example, cranes, a gearbox in a car) and in everyday life (scissors, wire cutters, scales, wrenches, etc.).
Block- this is a wheel with a groove around the circumference for a rope or chain, the axis of which is rigidly attached to a wall or ceiling beam. Lifting devices usually use not one, but several blocks. The system of blocks and cables, designed to increase the carrying capacity, is called a chain hoist.
gate- uh then two wheels connected together and rotating around the same axis, for example, a well gate with a handle.
Winch- a design consisting of two gates with intermediate gears in the drive mechanism.
Inclined plane used to move heavy objects to a higher level without directly lifting them.
Such devices include ramps, escalators, conventional stairs and conveyors.
Wedge- one of the varieties of a simple mechanism called "inclined plane". The wedge consists of two inclined planes, the bases of which are in contact. It is used to obtain a gain in strength, that is, with the help of a smaller force to counteract a larger force.
When chopping firewood, to facilitate the work, a metal wedge is inserted into the crack of the log and beaten on it with the butt of an ax.
Screw- an inclined plane wound on an axis. The thread of a screw is an inclined plane repeatedly wrapped around a cylinder. The ideal gain in strength given by the wedge is equal to the ratio of its length to the thickness at the blunt end. Real win the wedge is difficult to determine.
Due to the large friction, its efficiency is so small that the ideal gain has no special significance. Depending on the direction of rise of the inclined plane, the screw thread can be left or right.
Examples of simple devices with screw threads are a jack, a bolt with a nut, a micrometer, a vise.
On April 28, the scientific and practical conference of the NOU "Spectrum" will be held at the school.
A bit of history
A long time ago, back in 2005, my students and I at school organized the scientific society "Pythagorean", where we engaged in various activities from the analysis of Olympiad problems, to research work. Every year, involving other mathematicians of the school, they held conferences, then they took the children to conferences in Nalchik. Every year, our guys won prizes at the republican competitions. Everything was as it should be, we had our charter, program, requirements. At the end of the year, the results were summed up and each member of the NOU was awarded academic titles:
- "honorary academician" - winners and prize-winners of international and Russian, republican subject Olympiads, reviews, competitions;
- "academician" - winners of regional and city subject Olympiads, competitions, reviews;
- "master" - to the winners school olympiads, reviews, competitions;
- "Bachelor" - winners of school competitions, reviews, competitions.
Everyone knew about our society then. Buzzed. At a conference in Nalchik, we were once told that they could not give us prizes every time, not to submit many works for the competition. Which also played a role. When a member of the jury of a republican competition, in front of the children, says "Your works are the best, but we cannot give more than one place" ....
http://alfusja-bahova.ucoz.ru/index/nou_quot_pifagorenok_quot/0-5
By the way, all the guys who were then engaged in a scientific society easily entered the best technical universities in Moscow and St. this moment successfully graduated from universities. And one girl was left at the university in St. Petersburg (I can’t name the exact names of the universities right now). I'm proud of my guys.
But everything comes to an end. And our NOU too. No one paid me anything for this work, and as soon as they began to pay for it, "such a cow is needed by oneself", it turned out that our school did not need "Pythagorean", they created a new society "Spectrum", where everything is done "slipshod", I don't even want to talk about it.
After one unpleasant incident, she stopped taking part in school conferences with the guys.
And this year, I decided to go to the school conference with my circle members. We started the project on Wednesday. Let's see what happens.
At the next lesson of the circle, they began to research project"Lever. Types of levers. Leverage in human life."
The purpose and objectives of the research work:
- To study the device and the principle of operation of the lever;
- Assemble the "Lever" mechanism using Lego "Physics and Technology";
- Explore the properties of a lever. Find out the equilibrium condition of the lever;
- Questioning classmates;
- Explore the use of the lever in the home, at home, in technology, in sports and entertainment;
- Conclusions.
Did you know?
The term "lever" (English lever) comes from French word levier, which in translation means "to raise"
Since ancient times, to facilitate their work, a person has been using various mechanisms that are capable of transforming a person’s strength into a much greater strength. Three thousand years ago, during the construction of the pyramids in Ancient Egypt heavy stone slabs were moved and lifted using simple mechanisms.
A lever is a rigid rod or solid object that serves to transmit power. Using the lever, you can change the applied force (force), direction and distance of movement. In each lever, there is necessarily a force, a support (or an axis of rotation) and a load (load). Depending on their mutual arrangement, levers of the first, second and third kind are distinguished.
In this lesson, we dismantled the device and the principle of operation of the lever. With the help of Lego, three types of the "Lever" mechanism were assembled. Tried to do some research. We learned that any lever has a fulcrum, a point of application of force and a point of application of the load (i.e. load)
Types of levers
In levers of the first kind the fulcrum is located between the points of application of force and load.
The most common examples of a lever of the first kind are the saw, crowbar, pliers, and scissors.
In levers of the second kind the fulcrum and the force application point are at opposite ends, and the load application point is located between them. The most common examples of leverage of the second kind are nutcrackers, a wheelbarrow, and a bottle opener.
In levers of the third kind the fulcrum and the point of application of the load are at opposite ends, and the point of application of the force is between them. The best-known examples of leverage of the third kind are tweezers and ice tongs.
JavaScript is disabled in your browser
In the next lesson of the circle, we will continue our research.
PS. There are many great physicists on this site, I would be glad to receive advice and recommendations from you on our project. I won't turn down any help!
Levers are widespread in everyday life. It would be much more difficult for you to open a tightly screwed faucet if it did not have a 3-5 cm handle, which is a small but very effective lever. The same applies to a wrench, which you use to unscrew or tighten a bolt or nut. The longer the wrench, the easier it will be for you to unscrew this nut, or vice versa, the tighter you can tighten it. When working with especially large and heavy bolts and nuts, for example, when repairing various mechanisms, cars, machine tools, wrenches with a handle up to a meter are used.
Another striking example of a lever in everyday life is the most ordinary door. Try to open the door by pushing it near the hinges. The door will give in very hard. But the farther from the door hinges the point of application of force is located, the easier it will be for you to open the door.
Naturally, levers are also ubiquitous in technology. The most obvious example is the gear lever in a car. The short arm of the lever is the part that you see in the cabin. The long arm of the lever is hidden under the bottom of the car, and is about twice as long as the short one. When you shift the lever from one position to another, a long arm in the gearbox switches the corresponding mechanisms. Here you can also very clearly see how the length of the lever arm, the range of its travel and the force required to shift it correlate with each other.
Levers can be found at a construction site: an excavator, a crane, a wheelbarrow, a crowbar.
An example of a lever that gives a gain in strength is paper scissors, wire cutters, metal shears, a shovel.
Levers different kind many machines have: the handle of a sewing machine, the pedals or handbrake of a bicycle, the keys of a piano, are all examples of levers. Libra is also an example of a lever.
An example of a lever that gives a loss in strength is an oar. This is necessary to get a gain in distance. How longer part oars lowered into the water, the greater its radius of rotation and speed.
Thus, we can make sure that the lever mechanism is very widespread both in our daily life and in various mechanisms.
We have the right to say without exaggeration that each person is much stronger than himself, that is, that our muscles develop a force much greater than that which is manifested in our actions.
Is such a device appropriate? At first glance, as if not, we see here the loss of strength, which is not rewarded in any way. However, let us recall the old Golden Rule» mechanics: what is lost in strength is gained in movement. This is where the gain in speed comes in: our hands move 8 times faster than the muscles that control them. The way in which muscles are attached, which we see in animals, provides the limbs with agility of movement, more important in the struggle for existence than strength. We would be extremely slow creatures if our hands and feet were not arranged according to this principle.
"I could turn the Earth with a lever, just give me a fulcrum"
Archimedes
Lever arm- one of the most common and simple types of mechanisms in the world, present both in nature and in the world created by man.A lever is a rigid body that can rotate around some axis. A lever is not necessarily a long and thin object.
The human body as a lever
In the skeleton of animals and humans, all bones that have some freedom of movement are levers, for example, in humans - the bones of the limbs, the lower jaw, the skull, the phalanges of the fingers.
Let's take a look at the elbow joint. The radius and humerus are connected together by cartilage, and the muscles of the biceps and triceps are also attached to them. So we get the simplest lever mechanism.
If you hold a 3 kg dumbbell in your hand, how much effort does your muscle develop? The junction of the bone and muscle divides the bone in a ratio of 1 to 8, therefore, the muscle develops a force of 24 kg! It turns out that we are stronger than ourselves. But the lever system of our skeleton does not allow us to fully use our strength.
A good example of the better application of leverage to the musculoskeletal system is the reverse hind knee in many animals (all kinds of cats, horses, etc.).
Their bones are longer than ours, and the special structure of their hind legs allows them to use the strength of their muscles much more efficiently. Yes, of course, their muscles are much stronger than ours, but their weight is an order of magnitude greater.
The average horse weighs about 450 kg, and at the same time can easily jump to a height of about two meters. To perform such a jump, you and I need to be masters of sports in high jumps, although we weigh 8-9 times less than a horse.
Since we remembered the high jump, consider the options for using the lever, which were invented by man. The pole vault is a very good example.
With the help of a lever about three meters long (the length of the pole for high jumps is about five meters, therefore, the long arm of the lever, starting at the bend of the pole at the time of the jump, is about three meters) and the correct application of effort, the athlete takes off to a dizzying height of up to six meters.
Pick up a pen, write something or draw, and watch the pen and the movement of your fingers. You will soon discover that the handle is a lever. Find a foothold, evaluate your shoulders and make sure that in this case you lose in strength, but gain in speed and distance. Actually, when writing, the friction force of the stylus on the paper is small, so that the muscles of the fingers do not strain too much. But there are such types of work when the fingers must work to the fullest, overcoming significant forces, and at the same time make movements of exceptional accuracy: the fingers of a surgeon, a musician.
Lever in everyday life
Levers are also common in everyday life. It would be much more difficult for you to open a tightly screwed faucet if it did not have a 4-6 cm handle, which is a small but very effective lever.
The same applies to a wrench, which you use to unscrew or tighten a bolt or nut. The longer the wrench, the easier it will be for you to unscrew this nut, or vice versa, the tighter you can tighten it.
When working with especially large and heavy bolts and nuts, for example, when repairing various mechanisms, cars, machine tools, wrenches with a handle up to a meter are used.
Another striking example of leverage in everyday life is the most common door. Try to open the door by pushing it near the hinges. The door will give in very hard. But the farther from the door hinges the point of application of force is located, the easier it will be for you to open the door.
In plants, lever elements are less common, which is explained by the low mobility of the plant organism. A typical lever is a tree trunk and roots. A pine or oak root that goes deep into the ground offers tremendous resistance, so pines and oaks almost never turn upside down. On the contrary, spruces, which often have a superficial root system, tip over very easily.
The "piercing tools" of many animals and plants - claws, horns, teeth and thorns - are shaped like a wedge (a modified inclined plane); the pointed shape of the head of fast-moving fish is similar to a wedge. Many of these wedges have very smooth hard surfaces, which is what makes them so sharp.
Levers in technology
Naturally, levers are also ubiquitous in technology.
A simple "lever" mechanism has two varieties: block and gate.
With the help of a lever, a small force can balance a large force. Consider, for example, lifting a bucket from a well. The lever is a well gate - a log with a curved handle attached to it, or a wheel.
The axis of rotation of the gate passes through the log. The lesser force is the force of the person's hand, and the greater force is the force with which the bucket and the hanging part of the chain are pulled down.
Even before our Era, people began to use levers in the construction business. 
For example, in the picture you see the use of a lever when constructing a building. We already know that levers, blocks and presses allow you to get a gain in strength. However, is such a gain given "for nothing"?
When using a lever, its longer end travels a greater distance. Thus, having received a gain in strength, we get a loss in distance. This means that by lifting a large load with a small force, we are forced to make a large displacement.
The most obvious example is the gear lever in a car. The short lever arm is the part that you see in the cabin.
The long arm of the lever is hidden under the bottom of the car, and is about twice as long as the short one. When you shift the lever from one position to another, a long arm in the gearbox switches the corresponding mechanisms.
For example, in sports cars, for faster gear changes, the lever is usually set short, and its range is also made short.
However, in this case, the driver needs to make more effort to change gear. On the contrary, in heavy vehicles, where the mechanisms themselves are heavier, the lever is made longer, and its range of travel is also longer than in a passenger car.
A simple "inclined plane" mechanism and its two varieties - wedge and screw
An inclined plane is used to move heavy objects to a higher level without directly lifting them. If you need to lift a load to a height, it is always easier to use a gentle slope than a steep one. Moreover, the lower the slope, the easier it is to do this work.
A body on an inclined plane is held by a force that is ... in magnitude so many times less than the weight of this body, how many times the length of the inclined plane is greater than its height.
A wedge driven into a log acts on it from top to bottom. At the same time, he pushes the resulting halves to the left and right. That is, the wedge changes the direction of the force.
Thus, we can be convinced that the lever mechanism is very widespread both in nature and in our daily life, and in various mechanisms.
In addition, the force with which he pushes the halves of the log is much greater than the force with which the hammer acts on the wedge. Consequently, the wedge also changes the numerical value of the applied force.
Woodworking and garden tools represented a wedge - a plow, adze, scrapers, a shovel, a hoe. The land was cultivated with a plow, a harrow. Harvested with rakes, scythes, sickles.
A screw is a type of inclined plane. With it, you can get a significant gain in strength.
By turning the nut on the bolt, we raise it along an inclined plane and win in strength.
By turning the corkscrew handle clockwise, we cause the corkscrew screw to move down. Movement is transformed: rotary motion corkscrew leads to its forward movement.