How do pressure and resistance calculate friction
Publish: 2021-05-07 04:56:59
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2.
The only difference between resistance and friction is the concept
The force that hinders the relative motion or the trend of relative motion of an object is called frictionwhen one object slides on the surface of another, friction between contact surfaces hinders their relative motion, which is called sliding friction. The sliding friction is related to the roughness of the contact surface and the pressure. The larger the pressure is, the rougher the contact surface is, and the greater the sliding friction is
Resistance is an effective force. It can be simply understood as: the force that prevents physical movement is called resistance, and the force that promotes the movement of an object is called power. Resistance and power are antonyms of each othera train running on a straight railway is subject to the traction of the locomotive and the resistance of the air and the rail at the same time. The direction of traction and resistance is opposite, traction makes the train speed increase, while resistance makes the train speed decrease. If the traction and resistance balance each other, their effects on the train will cancel each other, and the train will keep moving in a uniform straight line
The characteristics of friction force are related to the objects that rub each other. Therefore, the description of friction force in physics is neither general nor accurate as other forces. Without friction, shoelaces can't be fastened, and screws and nails can't hold objects The biggest difference in friction is between static friction and other friction. Some people think that static friction should not actually be counted as friction. Other frictional forces are related to dissipation: it reces the relative velocity of objects that rub against each other and converts mechanical energy into heat energyan object moving relative to a fluid is resisted. This resistance is in the opposite direction of its motion. In the case of laminar flow, the resistance is proportional to its velocity. In turbulence, the resistance is proportional to the square of its velocity
sometimes an object is subject to resistance and friction at the same time, for example, a car is subject to both air resistance and rolling friction of its tires when it is moving Friction sometimes makes objects move, unlike resistance.)
Second, resistance e to the viscous effect of air, the surface of the object will proce friction tangent to the surface of the object, and the resultant force of all friction is called frictional resistance. The pressure difference resistance is the resistance formed by the airflow pressure perpendicular to the object surfacewithout considering viscosity and wake vortex (see lift line theory), the pressure drop of the body in subsonic flow is zero (see d'Alembert paradox). In the real fluid, the viscosity will not only proce friction resistance, but also make the pressure distribution on the surface different from that in the ideal fluid, and proce pressure resistance
3. The formula of sliding friction f = UN
where n is the pressure, and N = mg
u is the sliding friction coefficient on the horizontal ground, which is related to the material.
friction
1, friction
(1) definition: when two objects in contact with each other are about to move or have moved relative to each other, they will proce a force on the contact surface to hinder the relative movement, This kind of force is called friction.
(2) the friction between objects must have the following three conditions:
first, the objects contact and squeeze each other
Second, the contact surface is not smooth
Third, there is a relative movement trend or relative movement between objects.
2 Sliding friction force
(1) definition: the friction force generated when an object slides on the surface of another object is called sliding friction force.
(2) the experiment to study the relationship between the size of sliding friction force and which factors: why do we use the spring scale to pull the wood block to do uniform linear motion in the experiment? This is because the spring scale measures the tensile force, not the friction force. When the wood block moves in a straight line at a uniform speed, the horizontal tensile force of the wood block and the friction force of the board against the wood block are a pair of balance forces. According to the condition of the balance of the two forces, the tensile force should be equal to the friction force. Therefore, measuring the tensile force is also measuring the friction force, The greater the pressure is, the greater the sliding friction is; The coarser the contact surface is, the greater the sliding friction is.
(3) the sliding friction is the force that hinders the relative motion of objects in contact with each other, not necessarily the force that hinders the motion of objects, It should be clear that the object in contact with each other is used as the reference to hinder the "relative motion". The "object motion" may use other objects as the reference. For example, in the experiment, when a weight is placed on the wood block and the spring scale is used to pull the wood block to move at a uniform speed in a straight line, The specific situation is: when the wood block is pulled forward from static, the weight will slide backward relative to the wood block, and the wood block will give the weight a friction force to prevent it from sliding backward. The direction of the friction force is forward. Therefore, the weight does not slide relative to the wood block, In this case, the friction is static friction.
(4) the sliding friction has nothing to do with the speed of the motion of the object, and has nothing to do with the size of the contact area between objects.
(5) in order to simplify the practical problems, we often use the "idealized" method, such as one object is placed on the smooth surface of another object, which means that if two objects move relative to each other, the "smooth" method is used, There is no friction between them.
3. Static friction is proced by the interaction of two mutually stationary objects. The direction of static friction can be the same as or opposite to the direction of force.
4, Due to the deformation of two objects in contact, the rolling friction is called rolling friction
where n is the pressure, and N = mg
u is the sliding friction coefficient on the horizontal ground, which is related to the material.
friction
1, friction
(1) definition: when two objects in contact with each other are about to move or have moved relative to each other, they will proce a force on the contact surface to hinder the relative movement, This kind of force is called friction.
(2) the friction between objects must have the following three conditions:
first, the objects contact and squeeze each other
Second, the contact surface is not smooth
Third, there is a relative movement trend or relative movement between objects.
2 Sliding friction force
(1) definition: the friction force generated when an object slides on the surface of another object is called sliding friction force.
(2) the experiment to study the relationship between the size of sliding friction force and which factors: why do we use the spring scale to pull the wood block to do uniform linear motion in the experiment? This is because the spring scale measures the tensile force, not the friction force. When the wood block moves in a straight line at a uniform speed, the horizontal tensile force of the wood block and the friction force of the board against the wood block are a pair of balance forces. According to the condition of the balance of the two forces, the tensile force should be equal to the friction force. Therefore, measuring the tensile force is also measuring the friction force, The greater the pressure is, the greater the sliding friction is; The coarser the contact surface is, the greater the sliding friction is.
(3) the sliding friction is the force that hinders the relative motion of objects in contact with each other, not necessarily the force that hinders the motion of objects, It should be clear that the object in contact with each other is used as the reference to hinder the "relative motion". The "object motion" may use other objects as the reference. For example, in the experiment, when a weight is placed on the wood block and the spring scale is used to pull the wood block to move at a uniform speed in a straight line, The specific situation is: when the wood block is pulled forward from static, the weight will slide backward relative to the wood block, and the wood block will give the weight a friction force to prevent it from sliding backward. The direction of the friction force is forward. Therefore, the weight does not slide relative to the wood block, In this case, the friction is static friction.
(4) the sliding friction has nothing to do with the speed of the motion of the object, and has nothing to do with the size of the contact area between objects.
(5) in order to simplify the practical problems, we often use the "idealized" method, such as one object is placed on the smooth surface of another object, which means that if two objects move relative to each other, the "smooth" method is used, There is no friction between them.
3. Static friction is proced by the interaction of two mutually stationary objects. The direction of static friction can be the same as or opposite to the direction of force.
4, Due to the deformation of two objects in contact, the rolling friction is called rolling friction
4. When calculating the size of friction, we should first judge whether the friction is sliding friction or static friction. And then it is solved by the corresponding method
the calculation formula of sliding friction is f
= μ N
, where μ Dynamic friction coefficient, also called sliding friction coefficient, is only related to material and roughness of contact surface, but has nothing to do with contact area; N is the positive pressure
sliding friction: the force that occurs between two objects that contact each other and slide relatively, and prevents them from sliding relatively
the direction of friction is opposite to the direction of relative motion or the trend of relative motion. Instead of moving in the opposite direction of the object. Friction can be used as power or resistance.
the calculation formula of sliding friction is f
= μ N
, where μ Dynamic friction coefficient, also called sliding friction coefficient, is only related to material and roughness of contact surface, but has nothing to do with contact area; N is the positive pressure
sliding friction: the force that occurs between two objects that contact each other and slide relatively, and prevents them from sliding relatively
the direction of friction is opposite to the direction of relative motion or the trend of relative motion. Instead of moving in the opposite direction of the object. Friction can be used as power or resistance.
5. There are two kinds of friction: static and dynamic. Static is the amount of static friction you give it. Motion is friction, equal to the proct of friction factor and supporting force. The resistance of middle and primary schools generally involves friction resistance and safety compensation resistance
6. There is no specific formula for resistance, which should be obtained by force analysis; The calculation formula of sliding friction force is: F= μ F (friction factor times pressure)
7. Unknown_Error
8. It is required that the friction when the relative static (no sliding) is static friction, and the static friction is less than the maximum static friction (approximately equal to sliding friction). As long as it is within this range, the static friction f = external tension F
the friction force of relative sliding is f= μ FN among μ Is the antimagnetic friction coefficient between the contact surfaces of two objects. FN is the pressure between two objects.
the friction force of relative sliding is f= μ FN among μ Is the antimagnetic friction coefficient between the contact surfaces of two objects. FN is the pressure between two objects.
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