Types of mechanical movement. Body movement

Types of mechanical movement

Mechanical motion can be considered for different mechanical objects:

• Motion of a material point is completely determined by the change in its coordinates in time (for example, two on a plane). This is studied by the kinematics of a point. In particular, important characteristics of motion are the trajectory of a material point, displacement, speed and acceleration.
  • Straightforward motion of a point (when it is always on a straight line, the speed is parallel to this straight line)
  • Curvilinear movement- the movement of a point along a trajectory that is not a straight line, with arbitrary acceleration and arbitrary speed at any time (for example, movement in a circle).
• Rigid body motion consists of the movement of any of its points (for example, the center of mass) and the rotational movement around this point. Studied by rigid body kinematics.
  • If there is no rotation, then the movement is called progressive and is completely determined by the movement of the selected point. The movement is not necessarily linear.
  • For description rotational movement- body movements relative to a selected point, for example, fixed at a point, use Euler Angles. Their number in the case of three-dimensional space is three.
  • Also for solid allocate flat movement - movement in which the trajectories of all points lie in parallel planes, while it is completely determined by one of the sections of the body, and the section of the body is determined by the position of any two points.
• Continuum motion. Here it is assumed that the movement of individual particles of the medium is quite independent of each other (usually limited only by the conditions of continuity of velocity fields), therefore the number of defining coordinates is infinite (functions become unknown).

Geometry of movement

Relativity of motion

Relativity is the dependence of the mechanical motion of a body on the reference system. Without specifying the reference system, it makes no sense to talk about movement.

see also

Links

• Mechanical movement (video lesson, 10th grade program)

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See what “Mechanical movement” is in other dictionaries:

mechanical movement- Change over time in the relative position in space of material bodies or the relative position of parts of a given body. Notes 1. Within mechanics, mechanical motion can be briefly called motion. 2. The concept of mechanical movement... Technical Translator's Guide

mechanical movement- mechaninis judėjimas statusas T sritis fizika atitikmenys: engl. mechanical motion vok. mechanische Bewegung, f rus. mechanical movement, n pranc. mouvement mécanique, m … Fizikos terminų žodynas

mechanical movement- ▲ movement mechanical kinetics. kinetic. kinematics. mechanical processes processes of movement of material bodies. ↓ motionless, spreading, rolling...

mechanical movement- Change over time in the relative position in space of material bodies or the relative position of parts of a given body... Polytechnic terminological explanatory dictionary

MECHANICAL MOVEMENT OF POPULATION- MECHANICAL MOVEMENT OF POPULATION, decomp. types of territory moving us. The term M.D.S. appeared in the 2nd half. 19th century In modern scientific Literally, the term population migration is usually used... Demographic Encyclopedic Dictionary

movement of organisms- ▲ mechanical movement form of movement: amoeboid (amoeba, blood leukocytes). ciliated (flagellates, spermatozoa). muscular. ↓ muscle, movements (animal) ... Ideographic Dictionary of the Russian Language

movement- ▲ process of moving stationary movement process of moving. absolute movement. relative movement. ↓ move... Ideographic Dictionary of the Russian Language

Contents 1 Physics 2 Philosophy 3 Biology ... Wikipedia

In a broad sense, any change, in a narrow sense, a change in the position of a body in space. D. became a universal principle in the philosophy of Heraclitus (“everything flows”). The possibility of D. was denied by Parmenides and Zeno of Elea. Aristotle divided D. into... ... Philosophical Encyclopedia

Mechanical television is a type of television that uses electromechanical devices instead of electronic devices to decompose the image into elements. ray tubes. The very first television systems were mechanical and most often not... ... Wikipedia

Books

• Set of tables. Physics. 7th grade (20 tables), . Educational album of 20 sheets. Physical quantities. Measurements of physical quantities. Structure of matter. Molecules. Diffusion. Mutual attraction and repulsion of molecules. Three states of matter...

") around the 5th century. BC e. Apparently, one of the first objects of her research was a mechanical lifting machine, used in the theater to raise and lower actors portraying gods. This is where the name of science comes from.

People have long noticed that they live in a world of moving objects - trees sway, birds fly, ships sail, arrows fired from a bow hit targets. The reasons for such mysterious phenomena at that time occupied the minds of ancient and medieval scientists.

In 1638, Galileo Galilei wrote: “There is nothing more ancient in nature than movement, and philosophers have written many, many volumes about it.” The ancients and especially the scientists of the Middle Ages and the Renaissance (N. Copernicus, G. Galileo, I. Kepler, R. Descartes, etc.) already correctly interpreted certain issues of motion, but in general there was no clear understanding of the laws of motion in the time of Galileo.

The doctrine of the motion of bodies first appears as a strict, consistent science, built, like Euclid’s geometry, on truths that do not require proof (axioms), in Isaac Newton’s fundamental work “Mathematical Principles of Natural Philosophy,” published in 1687. Assessing the contribution to science scientist predecessors, the great Newton said: “If we have seen further than others, it is because we stood on the shoulders of giants.”

There is no movement in general, movement that is not related to anything, and there cannot be. The movement of bodies can only occur relative to other bodies and the spaces associated with them. Therefore, at the beginning of his work, Newton solves the fundamentally important question of space in relation to which the movement of bodies will be studied.

To give concreteness to this space, Newton associates with it a coordinate system consisting of three mutually perpendicular axes.

Newton introduces the concept of absolute space, which he defines as follows: “Absolute space, by its very essence, regardless of anything external, always remains the same and motionless.” The definition of space as motionless is identical to the assumption of the existence of an absolutely motionless coordinate system, relative to which the movement of material points and rigid bodies is considered.

Newton took as such a coordinate system heliocentric system, the beginning of which he placed in the center, and directed three imaginary mutually perpendicular axes to three “fixed” stars. But today it is known that there is nothing absolutely motionless in the world - it rotates around its axis and around the Sun, the Sun moves relative to the center of the Galaxy, the Galaxy - relative to the center of the world, etc.

Thus, strictly speaking, there is no absolutely fixed coordinate system. However, the motion of “fixed” stars relative to the Earth is so slow that for most problems solved by people on Earth, this motion can be neglected and the “fixed” stars can be considered truly motionless, and the absolutely motionless coordinate system proposed by Newton really exists.

In relation to an absolutely motionless coordinate system, Newton formulated his first law (axiom): “Every body continues to be maintained in its state of rest or uniform rectilinear motion until and unless it is forced by applied forces to change this state.”

Since then, attempts have been made and are being made to editorially improve Newton's formulation. One of the formulations sounds like this: “A body moving in space tends to maintain the magnitude and direction of its speed” (meaning that rest is movement with a speed equal to zero). Here the concept of one of the the most important characteristics movement - translational, or linear, speed. Typically linear speed is denoted by V.

Let us pay attention to the fact that Newton's first law speaks only about translational (linear) motion. However, everyone knows that there is another, more complex movement of bodies in the world - curvilinear, but more on that later...

The desire of bodies to “maintain their state” and “maintain the magnitude and direction of their speed” is called inertia, or inertia, tel. The word “inertia” is Latin; translated into Russian it means “rest”, “inaction”. It is interesting to note that inertia is an organic property of matter in general, “the innate force of matter,” as Newton said. It is characteristic not only of mechanical movement, but also of other natural phenomena, for example electrical, magnetic, thermal. Inertia manifests itself both in the life of society and in the behavior of individuals. But let's get back to the mechanics.

The measure of the inertia of a body during its translational motion is the mass of the body, usually denoted m. It has been established that during translational motion the magnitude of inertia is not affected by the distribution of mass within the volume occupied by the body. This gives grounds, when solving many problems in mechanics, to abstract from the specific dimensions of a body and replace it with a material point whose mass is equal to the mass of the body.

Location of this conditional point in the volume occupied by the body is called center of mass of the body, or, which is almost the same, but more familiar, center of gravity.

The measure of mechanical rectilinear motion, proposed by R. Descartes in 1644, is the amount of motion, defined as the product of the mass of a body by its linear speed: mV.

As a rule, moving bodies cannot maintain the same amount of momentum for a long time: fuel reserves are consumed in flight, reducing mass aircraft, trains slow down and accelerate, changing their speed. What reason causes the change in momentum? The answer to this question is given by Newton’s second law (axiom), which in its modern formulation sounds like this: the rate of change of momentum material point equal to the force acting on this point.

So, the reason that causes the movement of bodies (if at first mV = 0) or changes their momentum (if at first mV is not equal to O) relative to absolute space (Newton did not consider other spaces) are forces. These forces later received clarifying names - physical, or Newtonian, strength. They are usually designated F.

Newton himself gave the following definition of physical forces: “An applied force is an action performed on a body to change its state of rest or uniform linear motion.” There are many other definitions of strength. L. Cooper and E. Rogers, the authors of wonderful popular books on physics, avoiding boring strict definitions of force, introduce their definition with a certain amount of slyness: “Forces are what pulls and pushes.” It’s not completely clear, but some idea of ​​what strength is is emerging.

Physical forces include: forces, magnetic (see article ““), forces of elasticity and plasticity, resistance forces of the environment, light and many others.

If during the movement of a body its mass does not change (only this case will be considered further), then the formulation of Newton’s second law is significantly simplified: “The force acting on a material point is equal to the product of the mass of the point and the change in its speed.”

A change in the linear speed of a body or point (in magnitude or direction - remember this) is called linear acceleration body or point and is usually denoted a.

The accelerations and speeds with which bodies move relative to absolute space are called absolute accelerations And speeds.

In addition to the absolute coordinate system, one can imagine (with some assumptions, of course) other coordinate systems that move rectilinearly and uniformly relative to the absolute one. Since (according to Newton’s first law) rest and uniform rectilinear motion are equivalent, Newton’s laws are valid in such systems, in particular the first law - law of inertia. For this reason, coordinate systems moving uniformly and rectilinearly relative to the absolute system are called inertial coordinate systems.

However, in most practical problems, people are interested in the movement of bodies not relative to distant and intangible absolute space, or even relative to inertial spaces, but relative to other closer and completely material bodies, for example, a passenger relative to the body of a car. But these other bodies (and the spaces and coordinate systems associated with them) themselves move relative to absolute space non-rectilinearly and unevenly. The coordinate systems associated with such bodies are called mobile. For the first time, moving coordinate systems were used to solve complex tasks mechanics L. Euler (1707-1783).

We constantly encounter examples of the movement of bodies relative to other moving bodies in our lives. Ships sail across the seas and oceans, moving relative to the surface of the Earth, rotating in absolute space; a conductor serving tea throughout the compartment moves relative to the walls of a speeding passenger carriage; tea splashes out of a glass during sudden jolts of the carriage, etc.

To describe and study such complex phenomena, the concepts portable movement And relative motion and their corresponding portable and relative velocities and accelerations.

In the first of the examples given, the rotation of the Earth relative to absolute space will be a portable motion, and the movement of a ship relative to the surface of the Earth will be a relative motion.

To study the movement of a conductor relative to the walls of a car, you must first accept that the rotation of the Earth does not have a significant effect on the movement of the conductor and therefore the Earth can be considered stationary in this problem. Then the movement of the passenger car is portable movement, and the movement of the conductor relative to the car is relative motion. With relative motion, bodies influence each other either directly (by touching) or at a distance (for example, magnetic and gravitational interactions).

The nature of these influences is determined by Newton's third law (axiom). If we remember that physical strength, applied to bodies, Newton called action, then the third law can be formulated as follows: “Action is equal to reaction.” It should be noted that the action is applied to one, and the reaction is applied to the other of the two interacting bodies. Action and reaction are not balanced, but cause acceleration of interacting bodies, and the body whose mass is smaller moves with greater acceleration.

Let us also recall that Newton's third law, unlike the first two, is valid in any coordinate system, and not just in absolute or inertial ones.

In addition to rectilinear motion, curvilinear motion is widespread in nature, the simplest case of which is circular motion. We will consider only this case in the future, calling motion in a circle circular motion. Examples of circular motion: the rotation of the Earth around its axis, the movement of doors and swings, the rotation of countless wheels.

Circular motion of bodies and material points can occur either around axes or around points.

Circular motion (as well as rectilinear motion) can be absolute, figurative and relative.

Like rectilinear motion, circular motion is characterized by speed, acceleration, force factor, measure of inertia, and measure of motion. Quantitatively, all these characteristics are very strong degree depend on the distance from the axis of rotation of the rotating material point. This distance is called the radius of rotation and is denoted r .

In gyroscopic technology, angular momentum is usually called kinetic moment and is expressed through the characteristics of circular motion. Thus, the kinetic moment is the product of the moment of inertia of the body (relative to the axis of rotation) and its angular velocity.

Naturally, Newton's laws are also valid for circular motion. When applied to circular motion, these laws could be formulated somewhat simplistically as follows.

• First law: a rotating body strives to maintain relative to absolute space the magnitude and direction of its angular momentum (i.e., the magnitude and direction of its kinetic moment).
• Second law: the change in time of angular momentum (kinetic momentum) is equal to the applied torque.
• Third law: the moment of action is equal to the moment of reaction.

From school, everyone probably remembers what is called mechanical movement of the body. If not, then in this article we will try not only to remember this term, but also to update the basic knowledge from the physics course, or more precisely from the “Classical Mechanics” section. It will also show examples of how this concept is used not only in a certain discipline, but also in other sciences.

Mechanics

First, let's look at what this concept means. Mechanics is a branch of physics that studies the movement of various bodies, the interaction between them, as well as the influence of third forces and phenomena on these bodies. The movement of a car on the highway, the kicking of a soccer ball into the goal - all this is studied in this particular discipline. Usually, when using the term “Mechanics”, they mean “Classical mechanics”. What this is, we will discuss with you below.

Classical mechanics is divided into three large sections.

1. Kinematics - it studies the movement of bodies without considering the question of why they move? Here we are interested in such quantities as path, trajectory, displacement, speed.
2. The second section is dynamics. She studies the causes of movement, using concepts such as work, force, mass, pressure, impulse, energy.
3. And the third section, the smallest one, studies such a state as balance. It is divided into two parts. One illuminates the equilibrium of solids, and the second - liquids and gases.

Very often classical mechanics is called Newtonian mechanics, because it is based on Newton’s three laws.

Newton's three laws

They were first outlined by Isaac Newton in 1687.

1. The first law talks about the inertia of a body. This is a property in which the direction and speed of movement of a material point is preserved if no influence is applied to it. external forces.
2. The second law states that a body, acquiring acceleration, coincides with this acceleration in direction, but becomes dependent on its mass.
3. The third law states that the force of action is always equal to the force of reaction.

All three laws are axioms. In other words, these are postulates that do not require proof.

What is mechanical movement?

This is a change in the position of a body in space, relative to other bodies over time. In this case, material points interact according to the laws of mechanics.

Divided into several types:

• The movement of a material point is measured by finding its coordinates and tracking changes in coordinates over time. Finding these indicators means calculating the values ​​along the abscissa and ordinate axes. This is studied by the kinematics of a point, which operates with such concepts as trajectory, displacement, acceleration, and speed. The movement of the object can be rectilinear or curvilinear.
• The motion of a rigid body consists of the displacement of a point, taken as a basis, and rotational motion around it. Studied by the kinematics of rigid bodies. The movement can be translational, that is, rotation around given point does not occur, and the whole body moves uniformly, as well as flat - if the whole body moves parallel to the plane.
• There is also movement of a continuous medium. This is moving large quantity points connected only by some field or area. Due to the many moving bodies (or material points), one coordinate system is not enough here. Therefore, there are as many coordinate systems as there are bodies. An example of this is a wave on the sea. It is continuous, but consists of a large number of individual points on many coordinate systems. So it turns out that the movement of a wave is the movement of a continuous medium.

Relativity of motion

There is also such a concept in mechanics as relativity of motion. This is the influence of any reference system on mechanical motion. What does it mean? The reference system is the coordinate system plus the clock for Simply put, it is the x- and ordinate-axes combined with the minutes. Using such a system, it is determined during what period of time a material point has traveled a given distance. In other words, it has moved relative to the coordinate axis or other bodies.

The reference systems can be: comoving, inertial and non-inertial. Let's explain:

• Inertial CO is a system where bodies, producing what is called the mechanical motion of a material point, do it rectilinearly and uniformly or are generally at rest.
• Accordingly, a non-inertial CO is a system moving with acceleration or rotating relative to the first CO.
• The accompanying CO is a system that, together with a material point, performs what is called the mechanical movement of the body. In other words, where and at what speed an object moves, this CO also moves with it.

Material point

Why is the concept “body” sometimes used, and sometimes “material point”? The second case is indicated when the dimensions of the object itself can be neglected. That is, parameters such as mass, volume, etc., do not matter for solving the problem at hand. For example, if the goal is to find out how fast a pedestrian is moving relative to the planet Earth, then the height and weight of the pedestrian can be neglected. He is a material point. The mechanical movement of this object does not depend on its parameters.

Concepts and quantities of mechanical motion used

In mechanics, they operate with various quantities, with the help of which parameters are set, the conditions of problems are written, and a solution is found. Let's list them.

• A change in the location of a body (or a material point) relative to space (or a coordinate system) over time is called displacement. The mechanical movement of a body (material point), in fact, is a synonym for the concept of “movement”. It’s just that the second concept is used in kinematics, and the first in dynamics. The difference between these subsections has been explained above.
• A trajectory is a line along which a body (a material point) performs what is called mechanical motion. Its length is called the path.
• Velocity is the movement of any material point (body) relative to a given reporting system. The definition of the reporting system was also given above.

The unknown quantities used to determine mechanical motion are found in problems using the formula: S=U*T, where “S” is distance, “U” is speed, and “T” is time.

From the history

The very concept of “classical mechanics” appeared in ancient times, and was prompted by rapidly developing construction. Archimedes formulated and described the theorem on the addition of parallel forces and introduced the concept of “center of gravity.” This is how static began.

Thanks to Galileo, “Dynamics” began to develop in the 17th century. The law of inertia and the principle of relativity are his merit.

Isaac Newton, as mentioned above, introduced three laws that formed the basis of Newtonian mechanics. He also discovered the law of universal gravitation. This is how the foundations of classical mechanics were laid.

Nonclassical mechanics

With the development of physics as a science, and with the emergence of great opportunities in the fields of astronomy, chemistry, mathematics and other things, classical mechanics gradually became not the main one, but one of many in demand sciences. When concepts such as the speed of light, quantum field theory, and so on began to be actively introduced and operated, the laws underlying “Mechanics” began to be lacking.

Quantum mechanics is a branch of physics that deals with the study of ultra-small bodies (material points) in the form of atoms, molecules, electrons and photons. This discipline describes very well the properties of ultra-small particles. In addition, it predicts their behavior in a given situation, as well as depending on the impact. Predictions made by quantum mechanics can differ very significantly from the assumptions of classical mechanics, since the latter is not able to describe all phenomena and processes occurring at the level of molecules, atoms and other things - very small and invisible to the naked eye.

Relativistic mechanics is a branch of physics that deals with the study of processes, phenomena, as well as laws at speeds comparable to the speed of light. All events studied by this discipline occur in four-dimensional space, in contrast to the “classical” three-dimensional space. That is, to the height, width and length we add one more indicator - time.

What other definition of mechanical movement is there?

We covered only basic concepts related to physics. But the term itself is used not only in mechanics, be it classical or non-classical.

In the science called "Socio-economic statistics" the definition of mechanical movement of the population is given as migration. In other words, this is the movement of people over long distances, for example, to neighboring countries or to neighboring continents for the purpose of changing their place of residence. The reasons for such displacement may be the inability to continue living on their territory due to natural disasters, for example, constant floods or drought, economic and social problems in one’s own state, as well as the intervention of external forces, for example, war.

This article examines what is called mechanical motion. Examples are given not only from physics, but also from other sciences. This indicates that the term is ambiguous.

Mechanical movement is a change in the position of a body in space relative to other bodies.

For example, a car is moving along the road. There are people in the car. People move along with the car along the road. That is, people move in space relative to the road. But relative to the car itself, people do not move. This shows relativity of mechanical motion. Next we will briefly consider main types of mechanical movement.

Forward movement- this is the movement of a body in which all its points move equally.

For example, the same car makes forward motion along the road. More precisely, only the body of the car performs translational motion, while its wheels perform rotational motion.

Rotational movement is the movement of a body around a certain axis. With such a movement, all points of the body move in circles, the center of which is this axis.

The wheels we mentioned perform rotational motion around their axes, and at the same time, the wheels perform translational motion along with the car body. That is, the wheel makes a rotational movement relative to the axis, and a translational movement relative to the road.

Oscillatory motion- This is a periodic movement that occurs alternately in two opposite directions.

For example, oscillatory motion makes a pendulum in a clock.

Translational and rotational movements are the most simple types mechanical movement.

Relativity of mechanical motion

All bodies in the Universe move, so there are no bodies that are at absolute rest. For the same reason, it is possible to determine whether a body is moving or not only relative to some other body.

For example, a car is moving along the road. The road is located on planet Earth. The road is still. Therefore, it is possible to measure the speed of a car relative to a stationary road. But the road is stationary relative to the Earth. However, the Earth itself revolves around the Sun. Consequently, the road along with the car also revolves around the Sun. Consequently, the car makes not only translational motion, but also rotational motion (relative to the Sun). But relative to the Earth, the car makes only translational motion. This shows relativity of mechanical motion.

Relativity of mechanical motion– this is the dependence of the trajectory of the body, the distance traveled, movement and speed on the choice reference systems.

Material point

In many cases, the size of a body can be neglected, since the dimensions of this body are small compared to the distance that this body moves, or compared to the distance between this body and other bodies. To simplify calculations, such a body can conventionally be considered a material point that has the mass of this body.

Material point is a body whose dimensions can be neglected under given conditions.

The car we have mentioned many times can be taken as a material point relative to the Earth. But if a person moves inside this car, then it is no longer possible to neglect the size of the car.

As a rule, when solving problems in physics, we consider the movement of a body as motion of a material point, and operate with such concepts as the speed of a material point, the acceleration of a material point, the momentum of a material point, the inertia of a material point, etc.

Frame of reference

A material point moves relative to other bodies. The body in relation to which this mechanical movement is considered is called the body of reference. Reference body are chosen arbitrarily depending on the tasks to be solved.

Associated with the reference body coordinate system, which is the reference point (origin). The coordinate system has 1, 2 or 3 axes depending on the driving conditions. The position of a point on a line (1 axis), plane (2 axes) or in space (3 axes) is determined by one, two or three coordinates, respectively. To determine the position of the body in space at any moment in time, it is also necessary to set the beginning of the time count.

Frame of reference is a coordinate system, a reference body with which the coordinate system is associated, and a device for measuring time. The movement of the body is considered relative to the reference system. The same body has relative to different reference bodies in different systems coordinates can be completely different coordinates.

Trajectory of movement also depends on the choice of reference system.

Types of reference systems can be different, for example, a fixed reference system, a moving reference system, an inertial reference system, a non-inertial reference system.

Details Category: Mechanics Published 03/17/2014 18:55 Views: 15415

Mechanical movement is considered for material point and For solid body.

Motion of a material point

Forward movement an absolutely rigid body is a mechanical movement during which any straight line segment associated with this body is always parallel to itself at any moment in time.

If you mentally connect any two points of a solid body with a straight line, then the resulting segment will always be parallel to itself in the process forward motion.

During translational motion, all points of the body move equally. That is, they travel the same distance in the same amount of time and move in the same direction.

Examples of translational motion: the movement of an elevator car, mechanical scales, a sled rushing down a mountain, bicycle pedals, a train platform, engine pistons relative to the cylinders.

Rotational movement

During rotational motion, all points of the physical body move in circles. All these circles lie in planes parallel to each other. And the centers of rotation of all points are located on one fixed straight line, which is called axis of rotation. Circles that are described by points lie in parallel planes. And these planes are perpendicular to the axis of rotation.

Rotational movement is very common. Thus, the movement of points on the rim of a wheel is an example of rotational movement. Rotational motion is described by a fan propeller, etc.

Rotational motion is characterized by the following physical quantities: angular velocity of rotation, period of rotation, frequency of rotation, linear speed of a point.

Angular velocity A body rotating uniformly is called a value equal to the ratio of the angle of rotation to the period of time during which this rotation occurred.

The time it takes a body to complete one full revolution is called rotation period (T).

The number of revolutions a body makes per unit time is called speed (f).

Rotation frequency and period are related to each other by the relation T = 1/f.

If a point is located at a distance R from the center of rotation, then its linear speed is determined by the formula:

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