word "force" is so pervasive that give him a clear concept - a task almost impossible.A variety of muscle strength to strength of mind does not cover the whole range of concepts embedded in it.Strength, considered as a physical quantity that has a clearly defined meaning and definition.The formula defines a mathematical model of power: force versus basic parameters.

history research involves determining the force depending on the parameters and the experimental proof of dependency.

## Strength in Physics

Force - a measure of the interaction of bodies.The mutual action of bodies on each other fully describes the processes associated with changes in speed or deformation of the bodies.

as a physical quantity force is a unit of measurement (SI - Newton), and a device for measuring it - the dynamometer.Dynamometer operating principle is based on comparison of the force acting on the body with the elastic force of the spring dynamometer.

Over the force of 1 newton force is adopted, under the influence of which 1 kg of body weight changes its speed of 1 m for 1 second.

Strength is defined as a vector quantity:

- direction of action;
- point of application;
- module, an absolute value.

describing interaction necessarily indicate these parameters.

Types of natural interactions: gravitational, electromagnetic, strong, weak.Gravitational force (the force of gravity, with its variety - the force of gravity) exist due to the influence of gravitational fields surrounding any body having mass.Research fields Gravitation is not finished yet.Find the source of the field is not yet possible.

larger number of forces is caused by the electromagnetic interaction between atoms that make up matter.

## pressure force

The interaction of the body with the Earth, it exerts pressure on the surface.The pressure force, which is given by the formula: P = mg, defined by body mass (m).The acceleration of gravity (g) has different values at different latitudes of the Earth.

strength of the vertical pressure is equal in magnitude and opposite in direction to the elastic force arising in the support.Wherein Formula force varies depending on the movement of the body.

## change in body weight

Action to support the body due to the interaction with the Earth more frequently referred to as body weight.Interestingly, the body weight value dependent on the acceleration of movement in the vertical direction.In the case where the direction of acceleration is opposite to the acceleration of free fall, an increase in weight.If acceleration of the body coincides with the direction of gravity, the body weight reduced.For example, while in a lift, at the beginning of lifting a person feels the weight gain for some time.To claim that its mass is changing, however.At the same time we share the concept of "weight" and "mass".

## resilient force

Changing body shape (deformation) occurs force that tends to return the body to its original shape.This force was given the name "elastic force".There is it due to electrostatic interaction between the particles that make up the body.

Consider a simple strain: tension and compression.Stretching accompanied by an increase of linear dimensions of bodies, compression - reducing them.Quantities characterizing these processes, called extension of the body.Let it "x".Formula elastic force is directly related to the elongation.Each body undergoing deformation has its own geometrical and physical parameters.The dependence of the elastic deformation resistance of the body and on the properties of the material from which it is made is determined by the coefficient of elasticity, we call it rigidity (k).

mathematical model of elastic interaction is described by Hooke's law.

force generated by the deformation of the body, is directed against the direction of displacement of the individual parts of the body is directly proportional to its elongation:

- Fy = -kx (in vector notation).

sign "-" indicates the opposite direction of deformation and strength.

In scalar form a negative sign is missing.The resilient force, the formula of which is as follows Fy = kx, used only when the elastic deformations.

## interaction of the magnetic field with a current

influence of magnetic field on DC described by Ampere.The force with which the magnetic field acts on a current-carrying conductor placed in it, called the Ampere force.

interaction of the magnetic field with a moving electric charge is a manifestation of the force.Ampere's formula which has the form F = IBlsinα, depends on the magnetic induction field (B), the active part length of the conductor (l), current (I) in the conductor and the angle between the current direction and magnetic induction.

Thanks to the latest depending on it can be argued that the vector of the magnetic field may change when turning or changing direction of conductor current.Left Hand Rule allows you to set the direction of action.If the left hand positioned in such a way that the magnetic induction vector was a palm, four fingers were directed current in the conductor, then bent by 90 ° thumb show the direction of the magnetic field.

Use of this impact mankind is found, for example, in electric motors.The rotation of the rotor caused by the magnetic field created by powerful electromagnets.Formula power to judge the possibility of changing the engine power.With increasing the power or magnitude of the field torque increases, thereby increasing engine power.

## particle trajectories

interaction of the magnetic field with a charge widely used in mass-spectrographs in the study of elementary particles.

Action in this field causes a force, called the Lorentz force.When injected into the magnetic field is moving with a velocity of a charged particle Lorentz force, which is given by the formula F = vBqsinα, causes the movement of particles in a circle.

In this mathematical model v - unit of the particle velocity, electric charge which - q, B - magnetic induction field, α - the angle between the velocity and magnetic induction.

particle moves in a circle (or arc of a circle), as strength and speed are directed at 90 ° to each other.Changing the direction of the linear velocity causes acceleration.

left hand rule discussed above, takes place in the study of the Lorentz force, if the left arm positioned so that the magnetic induction vector was a palm, four fingers extending in a line have been sent to the speed of a positively charged particle, then bent on90 ° thumb shows the direction of the force.

## Problems plasma

interaction of the magnetic field and the substance used in cyclotrons.Problems associated with the laboratory study of plasma do not allow keep it in closed vessels.Highly ionized gas can exist only at high temperatures.Confine the plasma in one location space is possible by means of magnetic fields, the spinning gas to a ring.Controlled thermonuclear reactions can be studied as spinning high-temperature plasma in the cord by means of magnetic fields.

example of the magnetic field in natural conditions in the ionized gas - Aurora.This majestic sight is observed in the Arctic Circle at an altitude of 100 km above the ground.Mysterious colorful glowing gas could explain only in the twentieth century.The magnetic field near the poles of the earth can not prevent the penetration of the solar wind in the atmosphere.The most active radiation is directed along the lines of magnetic induction, causing ionization of the atmosphere.

## phenomena associated with the movement of the charge

Historically, the main quantity characterizing the flow of current in a conductor is called current.Interestingly, this concept is nothing to do with the power of physics has.The strength of the current formula which includes the charge flowing per unit time through a cross-section has the form:

- I = q / t, where t - time flow of charge q.

In fact, the current - the magnitude of the charge.The units of measurement is ampere (A), in contrast to H.

## some work force

force on the substance followed by the performance of work.The work force - a physical quantity that is numerically equal to the product of the forces on the move, traveled under its action, and the cosine of the angle between the force and displacement.

Seeking work force, the formula has the form A = FScosα, includes the amount of force.

Action is accompanied by a change in the speed of the body or body deformation, indicating that a simultaneous change of energy.Work force depends on the magnitude.