What mechanisms give a gain in strength. Simple mechanisms around us

"Simple mechanisms in everyday life" - A simple mechanism "inclined plane". simple mechanisms in technology. Lever arm. Inclined plane. Gate. To get acquainted with the practical application of simple mechanisms. Wedge. Winch. Experiment. Tower cranes. Simple mechanisms in nature. Systematize the acquired knowledge. Screw. Puzzles. Means of siege.

"Simple mechanisms" - Klin. Conclusion. Inventions of Archimedes. simple mechanisms. Screw. Gear. Simple mechanisms used by us in life. Lever arm. Archimedes. Wheel. Since ancient times, man has learned to use the lever to lift weights. Plan for studying the topic. Block. Therefore, for a moving block, the ideal gain in strength is 2.

"Application of simple mechanisms" - Simple mechanisms. Run test. Gain in strength, but loss in movement. In sports. Lever arm. Sports. Prepare a short message or presentation on the use of leverage. Make a crossword puzzle on this topic. Rescuer tools. Technique. Creative task: I option. And in force? In technology.

"Simple mechanisms Grade 7" - Techniques are demonstrated pilot study using didactic materials. Assessment and standards. Teacher presentation. Project site: Control is carried out in several directions. Students' work. Project planning. Work in the computer science office outside of school hours. Project theme: "Simple mechanisms".

"Golden Rule of Mechanics" - "Golden" Rule of Mechanics". Block. None of the simple mechanisms gives a gain in work. What is called a simple mechanism. How many times have we won in strength. Using a lever, they lifted the load to a height of 8 cm. Where a person uses simple mechanisms in his life. Wedge. Inclined plane. The purpose of our lesson

"Cam mechanism" - Cam system and related mechanisms. Manual drive of the machine. The fundamental tones of closed pipes are an octave lower than open ones. Brugger's mechanical organ. The most common are labial tubes. Reed pipes. Curator of the collection of jukeboxes at the Polytechnic Museum. On the monuments of science and technology of the Polytechnic Museum.

In total there are 8 presentations in the topic

SIMPLE MECHANISMS

In addition to the lever and the block, simple mechanisms also include an inclined plane and its varieties: a wedge and a screw.

INCLINED PLANE

Inclined plane used to move heavy objects for more than high level without directly lifting them.
Such devices include ramps, escalators, conventional stairs and conveyors.
If you need to lift the load to a height, it is always easier to use a gentle slope than a steep one. Moreover, the flatter the slope, the easier it is to do this work. When time and distance do not matter much, but it is important to lift the load with the least effort the inclined plane is indispensable.

With the help of these drawings, you can explain how a simple mechanism works. INCLINED PLANE.
Classic Action Calculations inclined plane and other simple mechanisms belong to the outstanding antique mechanic Archimedes from Syracuse.

During the construction of temples, the Egyptians transported, lifted and installed colossal obelisks and statues, the weight of which was tens and hundreds of tons! All this could be done using among other simple mechanisms inclined plane.
The main lifting device of the Egyptians was inclined plane - ramp. The skeleton of the ramp, that is, its sides and partitions, which crossed the ramp at a short distance from each other, were built of brick; voids were filled with reeds and branches. As the pyramid grows the ramp was built up. On these ramps, stones were dragged on sleds in the same way as on the ground, while helping themselves with levers. The ramp angle was very slight - 5 or 6 degrees.

Columns of the ancient Egyptian temple in Thebes.

Each of these huge columns was dragged by slaves along a ramp - an inclined plane. When the column crawled into the pit, sand was raked out through the hole, and then the brick wall was dismantled and the embankment was removed. Thus, for example, the sloping road to the pyramid of Khafre, with an elevation of 46 meters, had about half a kilometer long.

"A body on an inclined plane is held by a force that ... is so many times less in magnitude than the weight of this body, how many times the length of the inclined plane is greater than its height."
it condition for the balance of forces on an inclined plane formulated by the Dutch scientist Simon Stevin (1548-1620).

Drawing on title page S. Stevin's books, with which he confirms his formulation.

The inclined plane at the Krasnoyarsk hydroelectric power station is very ingeniously used. Here, instead of gateways, shipping chamber moving along an inclined overpass. For its movement, a traction force of 4000 kN is required.

And why do mountain roads wind in a gentle "serpentine"?

Wedge- one of the varieties of a simple mechanism called "inclined plane". The wedge consists from two inclined planes whose bases 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.
The ideal gain in force given by the wedge is equal to the ratio of its length to the thickness at the blunt end. Due to the high friction, its efficiency is so small that the ideal gain does not really matter.

Another type of inclined plane is the screw.
Screw - inclined plane, wound on an axle. 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. The real payoff of a wedge is difficult to determine.
Due to the high friction, its efficiency is so small that the ideal gain does not matter much. 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 − jack, bolt with nut, micrometer, vise.

Other pages on physics topics for grade 7:

"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.They call it a lever solid, which 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 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.

Already in ancient times, people began to use simple mechanisms for lifting weights: a lever, a gate and an inclined plane. Later, a block and a screw were added to them. These simple devices made it possible to multiply the muscular efforts of a person and to cope with such weights that, under other circumstances, would be completely unbearable. The principle of operation of simple mechanisms is well known. For example, if you need to pull a load to a certain 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. This relationship has a clear mathematical expression. If the inclined plane has an angle d, then it will be 1/sin d times easier to drag the load along it than to lift it vertically. If the angle is 45 degrees, our effort will be 1.5 times less, if 30 degrees - 2 times less, with an angle of 5 degrees we will spend 11 times less effort, and with an angle of 1 degree - 57 times! True, everything that is gained in strength is lost in distance, for by how many times our effort is reduced, by the same number of times the distance over which the load will have to be dragged increases. However, in cases where time and distance do not play a big role, but the goal itself is important - to lift the load with the least effort, the inclined plane turns out to be an indispensable assistant. Another simple mechanism - a lever - our distant ancestors constantly used to lift and move heavy stones and logs. The lever allows you to achieve a multiple gain in strength by the simplest and most affordable means. Putting a long and strong pole on a log stump (support) and slipping its second end under a stone, a person turned the pole into the simplest lever. In this situation, two torques began to act on the stone, one from the weight of the stone, and the other from the hand of a person. In order for the stone to move, the “pushing” moment from the muscular strength of a person must be greater than the “pressing” moment from the weight of the stone. The moment, as you know, is equal to the product of the applied force and the length of the lever arm (in this case, the arm is the distance from the end of the pole (point of application of force) to the log (fulcrum)). It is easy to calculate that if the shoulder on which the person presses is 15-20 times longer than the one that is slipped under the stone, then the strength of the person, respectively, also increases by 15-20 times. That is, a person, without really straining, can move a stone weighing a ton! The fixed block - the third mechanism that became widespread in antiquity - is a wheel with a chute, the axis of which is rigidly attached to a wall or ceiling beam. Throwing a rope over the wheel and attaching its opposite end to the load, you can raise it to the height of the block attachment. A fixed block does not give a gain in strength, but it does provide an opportunity to change its direction, which is often of great importance when lifting weights.

For all their primitiveness, simple mechanisms greatly expanded the capabilities of ancient man. In order to be convinced of this, it is enough to recall the gigantic buildings of the ancient Egyptians. For example, the Cheops pyramid had a height of 146 m. It is estimated that 23,300,000 stone blocks were required for its construction, each of which weighed an average of about 2.5 tons. But this was not the limit - during the construction of temples, the Egyptians transported, raised and installed colossal obelisks and statues, the weight of which was tens and hundreds of tons! What mechanisms did these ancient builders use to raise gigantic blocks and statues to a great height? It turns out that all this can be done using the same simple devices - a block, levers and an inclined plane. Colossal statues and blocks of stone were dragged on massive sledges pulled by a large number of people. Each of the workers had a rope thrown over his shoulder. Rollers were placed under the sled, which, after pulling the load, were picked up and again placed under the skids. To overcome obstacles, the sled was lifted with the help of levers. As they used hewn logs. Specially made wedges of different sizes served as stops. The work was accompanied by music. The main lifting device of the Egyptians was an inclined plane - a ramp. The skeleton of the ramp, that is, its sides and partitions, which crossed the ramp at a short distance from each other, were built of brick; voids were filled with reeds and branches. As the pyramid grew, the ramp was built on. On these ramps, stones were dragged on sleds in the same way as on the ground, while helping themselves with levers. The ramp angle was very slight - 5 or 6 degrees. Thus, for example, the sloping road to the pyramid of Khafre, with a height of 46 meters, had a length of about half a kilometer. Accordingly, for the construction of higher pyramids, it was necessary to build a ramp even longer.

Other methods were resorted to when lifting long stone blocks and statues. Blocks were used for this. However, it is impossible to raise huge stones with the help of blocks, such as obelisks up to 300 tons in weight and giant statues of kings, reaching 1000 tons in weight, it is impossible. To install such statues and obelisks, considerable preparatory work had to be carried out. Here again, an inclined plane - a ramp - acted as a lifting device. First of all, stone walls were erected on both sides of the pedestal. An inclined plane was attached to one of them, a little less than the height of the installed obelisk. All four walls of the ramp formed, as it were, a brick well. A through corridor was made in one of its walls at ground level. The entire space inside was covered with sand. Then, along the inclined plane, the completed obelisk was dragged with the base forward. After that, sand began to be carried out through the corridor in the wall, and the obelisk, under its own weight, began to smoothly descend onto the pedestal, gradually assuming a vertical position. After installation, the wall and ramp were dismantled.

With extensive use of the inclined plane and the lever, the ancient Egyptians seem to have given no thought to the laws that underlie simple mechanisms. At least not a single Babylonian or Egyptian text has come down to us describing their action. This work was carried out only by scientists Ancient Greece. Classical calculations of the action of a lever, an inclined plane and a block belong to the outstanding ancient mechanic Archimedes of Syracuse. Archimedes studied the mechanical properties of the moving block and put it into practice. According to Athenaeus, “many methods were invented to launch the gigantic ship built by the Syracusan tyrant Hieron, but the mechanic Archimedes alone managed to move the ship with the help of a few people; Archimedes arranged a block and through it launched a huge ship; he was the first to invent the device of the block. From this evidence it is clear that Archimedes not only studied the properties of simple mechanisms, but also took the next step - he began to build more complex machines on their basis that transform and enhance movement. It is possible that he managed to move the ship with the help of a system of movable and fixed blocks (similar to modern hoists), using which you can multiply the applied force. When on native city Archimedes was attacked by the Romans, he applied his knowledge in military equipment. According to his drawings, the Syracusans built a wide variety of military vehicles. Among them were throwing weapons; swivel cranes that hurled huge stones onto Roman ships; iron paws tied to chains that captured and overturned enemy ships.

The principle of operation of simple mechanisms is well known. For example, if you need to pull a load to a certain 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. This relationship has a clear mathematical expression. If the inclined plane has an angle d, then it will be 1/sin d times easier to drag the load along it than to lift it vertically. If the angle is 45 degrees, our effort will be 1.5 times less, if 30 degrees - 2 times less, with an angle of 5 degrees we will spend 11 times less effort, and with an angle of 1 degree - 57 times!

True, everything that is gained in strength is lost in distance, for by how many times our effort is reduced, by the same number of times the distance over which the load will have to be dragged increases. However, in cases where time and distance do not play a big role, but the goal itself is important - to lift the load with the least effort, the inclined plane turns out to be an indispensable assistant.

Inclined plane

Another simple mechanism - a lever - our distant ancestors constantly used to lift and move heavy stones and logs. The lever allows you to achieve a multiple gain in strength by the simplest and most affordable means. Putting a long and strong pole on a log stump (support) and slipping its other end under a stone, a person turned the pole into a simple lever. In this situation, two torques began to act on the stone, one from the weight of the stone, and the other from the hand of a person. In order for the stone to move, the "pushing" moment from the muscular strength of a person must be greater than the "pressing" moment from the weight of the stone. The moment, as you know, is equal to the product of the applied force and the length of the arm of the lever - in this case, the arm is the distance from the end of the pole (the point of application of force) to the log (the fulcrum).

Lever arm

It is easy to calculate that if the shoulder on which the person presses is 15-20 times longer than the one that is slipped under the stone, then the strength of the person, respectively, also increases by 15-20 times. That is, a person, without really straining, can move a stone weighing a ton!

The fixed block - the third mechanism that became widespread in antiquity - is a wheel with a chute, the axis of which is rigidly attached to a wall or ceiling beam. Throwing a rope over the wheel and attaching its opposite end to the load, you can raise it to the height of the block attachment. A fixed block does not give a gain in strength, but it does provide an opportunity to change its direction, which is often of great importance when lifting weights.

Fixed block

What mechanisms did these ancient builders use to raise gigantic blocks and statues to a great height? It turns out that all this can be done using the same simple devices - a block, levers and an inclined plane. Colossal statues and blocks of stone were dragged on massive sledges pulled by a large number of people. Each of the workers had a rope thrown over his shoulder. Rollers were placed under the sled, which, after pulling the load, were picked up and again placed under the skids.

Wooden block of ancient Egyptians

To overcome obstacles, the sled was lifted with the help of levers. As they used hewn logs. Specially made wedges of different sizes served as stops. The work was accompanied by music. The main lifting device of the Egyptians was an inclined plane - a ramp. The skeleton of the ramp, that is, its sides and partitions, which crossed the ramp at a short distance from each other, were built of brick; voids were filled with reeds and branches.

As the pyramid grew, the ramp was built on. On these ramps, stones were dragged on sleds in the same way as on the ground, while helping themselves with levers. The ramp angle was very slight - 5 or 6 degrees. Thus, for example, the sloping road to the pyramid of Khafre, with a height of 46 meters, had a length of about half a kilometer. Accordingly, for the construction of higher pyramids, it was necessary to build a ramp even longer.

To install such statues and obelisks, considerable preparatory work had to be carried out. Here again, an inclined plane - a ramp - acted as a lifting device. First of all, stone walls were erected on both sides of the pedestal. An inclined plane was attached to one of them, a little less than the height of the installed obelisk. All four walls of the ramp formed, as it were, a brick well. A through corridor was made in one of its walls at ground level. The entire space inside was covered with sand. Then, along the inclined plane, the completed obelisk was dragged with the base forward. After that, sand began to be carried out through the corridor in the wall, and the obelisk, under its own weight, began to smoothly descend onto the pedestal, gradually assuming a vertical position. After installation, the wall and ramp were dismantled.

From this evidence it is clear that Archimedes not only studied the properties of simple mechanisms, but also took the next step - he began to build more complex machines on their basis that transform and enhance movement. It is possible that he managed to move the ship with the help of a system of movable and fixed blocks (similar to modern hoists), using which you can multiply the applied force.

When the Romans attacked Archimedes' hometown, he applied his knowledge to military technology. According to his drawings, the Syracusans built a wide variety of military vehicles. Among them were throwing weapons; swivel cranes that hurled huge stones onto Roman ships; iron paws tied to chains that captured and overturned enemy ships.

What mechanisms give a gain in strength. Simple mechanisms around us - write to Antoshka

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