How to calculate the friction force with two contact surfaces
Publish: 2021-05-05 08:03:08
1. Before calculating the friction force, we must first analyze the motion of the object to determine whether it is static friction or sliding friction. If it is sliding friction, the formula
F
can be used= μ N
calculation, where μ
is the friction coefficient; If it is static friction, it is usually solved according to the motion of the object (static, uniform motion, or variable speed motion) by using the equilibrium condition or the law of motion
to determine the direction of sliding friction, we must grasp the judgment basis of "the direction of sliding friction is opposite to the relative motion direction of the object". The specific method is: first select the object subject to friction as the research object, and then take the object in direct contact with the research object as the reference object, find out the speed direction of the research object relative to the reference object, then the direction of sliding friction is opposite to the direction of the relative speed
the basis for judging the direction of static friction is: "the direction of static friction is always tangent to the contact surface, and is opposite to the direction of relative motion trend of the object". The specific method is: firstly, select the object subject to static friction as the research object, and then select the object in contact with the research object as the reference object, and then assume that the contact surface is smooth to judge the velocity direction of the research object relative to the reference object, that is, the relative motion trend direction. Then, the direction of static friction is opposite to the direction of relative motion trend.
F
can be used= μ N
calculation, where μ
is the friction coefficient; If it is static friction, it is usually solved according to the motion of the object (static, uniform motion, or variable speed motion) by using the equilibrium condition or the law of motion
to determine the direction of sliding friction, we must grasp the judgment basis of "the direction of sliding friction is opposite to the relative motion direction of the object". The specific method is: first select the object subject to friction as the research object, and then take the object in direct contact with the research object as the reference object, find out the speed direction of the research object relative to the reference object, then the direction of sliding friction is opposite to the direction of the relative speed
the basis for judging the direction of static friction is: "the direction of static friction is always tangent to the contact surface, and is opposite to the direction of relative motion trend of the object". The specific method is: firstly, select the object subject to static friction as the research object, and then select the object in contact with the research object as the reference object, and then assume that the contact surface is smooth to judge the velocity direction of the research object relative to the reference object, that is, the relative motion trend direction. Then, the direction of static friction is opposite to the direction of relative motion trend.
2. 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
3. The acceleration of the object below is affected by the friction of the upper surface and the lower surface. The friction of the upper surface is equal to the friction of the object above, and the direction is opposite. The friction of the lower surface is related to the gravity of the two objects (that is, the pressure on the table). Then the acceleration can be obtained by analyzing the stress of the object below
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Global Express is Alibaba's online trading platform for the global market, which is known as the international version of "Taobao" by the majority of sellers
just like Taobao, you can edit your baby into online information and publish it overseas through the express platform. Similar to the domestic delivery process, the baby is transported to the buyer through international express delivery. In this way, it is easy to enter into transactions with buyers from more than 220 countries and regions and earn US dollars. However, in order to protect domestic e-commerce and restrict or prohibit cross-border online shopping, Russia and Argentina have implemented corresponding policies.
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