At the bar there are gravitational force F cord and the normal force is perpendicular to the surfac

With the phenomenon of friction person found daily in the workplace: in some cases it reduces it in others - increases. Friction accompanies every movement of the body or resting flv to state. It occurs in direct osculation bodies and always directed along the surface of osculation.
At the bar there are gravitational force F cord and the normal force is perpendicular to the surface of the bar force F, applied to the bar to move it up and the friction force F in May, directed against the movement of the body. Pulling the dynamometer, the spring is stretched it to this tension can be seen on the force that must be applied to the body to move it from the spot.
Force static friction force is called, which must be applied to the body to move it from place May F max = μN, ie the maximum static friction force is proportional to the strength of normal pressure, but there are times when it is static friction force is the cause of motion. When walking it is static friction force acting on the sole provides individual acceleration and the force directed in the opposite direction it provides acceleration of the Earth, and by Newton's third law action is equal and opposite reaction.
The wheels of cars, trams, trolley buses, tractors, tanks, building on the ground, moving forward flv to and this "repulsive force" and is the force of static friction. In a belt drive pulley acceleration also gives force of static friction.
If the bar to put the power and pull it evenly in a straight line, then show the strength dynamometer friction. This force is always directed opposite to the direction of motion of the body relative to the surface on which it moves. Direction of the friction force opposite to the movement of the body, and therefore the friction always results in a decrease in the rate of the body.
But the friction force depends on the direction of more speed because of the change of direction of the friction force is also changing sliding friction is always greater than rolling friction and therefore try, if possible, replace the friction force on force friction bearings (bearings), because the body is always easier perekotyty than drag.
Force called rolling friction force that occurs when the rolling flv to of one body on the surface of another. The cause of the friction force is the surface roughness, no matter flv to how smooth it is we do not give up. Even in the ideal case, the mirror surfaces, each surface atom becomes inequality. These surface of bodies stick to each other and become as strong as welding (ie stick).
Friction without lubrication between solid bodies called dry friction. To reduce the friction force using solid oil lubrication of the rubbing surfaces, lubricating oil, graphite grease, paraffin. And to increase the friction of the road and sidewalks sprinkled flv to with sand, place the chains on tires, winter tires with studs are used, and set the correct sign on the windows flv to machine, pour sand on the tram rails to the front wheels if they are covered with ice, etc.
If a rigid body moving in a liquid or gas, between it and the liquid flv to or gas is rarely friction, which is called impedance. For example, the combustion of meteorites in the Earth's atmosphere, heating the plating spacecraft during launch and landing, flv to the melting of ice at the skating and so on.
If you have already registered as a commentator flv to or wish to register, enter a password and a valid e-mail. When you register at the specified address will come letter with an activation code and a link to your personal account where you can change your details, including your site alias, description, contacts and so on and subscribe to new comments.

Mathematics for School flv to Mathematics for School Mathematics Zanymatelnaya Zanymatelnыe Mathematical facts, Formula, solutions Problem popular science magazine Piznavayka of Cognitive Science flv to