How to calculate the friction force when the mass is equal in Ph
Publish: 2021-05-06 08:22:18
1. You can't withdraw money, can you? help
2. Friction refers to the force that hinders the relative motion (or relative motion trend) of an object. Its direction is opposite to the relative motion (or relative motion trend) of the object. Friction is divided into static friction, rolling friction and 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
friction is related to objects that rub against each other, so the description of friction in physics is not general, nor is it as 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 energy< The friction between solid surfaces can be divided into sliding friction, rolling friction, static friction, rolling friction and rotational friction. In engineering technology, people use lubricating oil to rece friction. If two surfaces are separated by a layer of liquid, liquid friction can occur between them. If the separation of liquid is not complete, mixed friction may also occur. Air track works by air friction. The working principle of lubricating oil and air track is to use "liquid or gas (i.e. fluid) friction to replace solid friction" to work
If lubricating oil, liquid or gas flows along a solid surface, its velocity will be reced e to the influence of friction. The structure of the solid surface has little effect on the friction, and the most important one is the cross-sectional area of the fluid. The reason is that there is friction not only at the interface between the fluid and the solid, but also between different layers in the fluid, and the velocity of the fluid varies with the distance from the solid surface
an 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, when a car is moving, it is subject to the resistance of air and the rolling friction of its tires Friction sometimes makes objects move, unlike resistance.)
friction is related to objects that rub against each other, so the description of friction in physics is not general, nor is it as 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 energy< The friction between solid surfaces can be divided into sliding friction, rolling friction, static friction, rolling friction and rotational friction. In engineering technology, people use lubricating oil to rece friction. If two surfaces are separated by a layer of liquid, liquid friction can occur between them. If the separation of liquid is not complete, mixed friction may also occur. Air track works by air friction. The working principle of lubricating oil and air track is to use "liquid or gas (i.e. fluid) friction to replace solid friction" to work
If lubricating oil, liquid or gas flows along a solid surface, its velocity will be reced e to the influence of friction. The structure of the solid surface has little effect on the friction, and the most important one is the cross-sectional area of the fluid. The reason is that there is friction not only at the interface between the fluid and the solid, but also between different layers in the fluid, and the velocity of the fluid varies with the distance from the solid surface
an 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, when a car is moving, it is subject to the resistance of air and the rolling friction of its tires Friction sometimes makes objects move, unlike resistance.)
3. To solve the problem of friction, you must understand the concept of friction, that is, the conditions under which friction occurs
the so-called friction is the force that hinders the relative motion of an object, and the direction of friction is opposite to the motion direction or relative motion direction of the object
the conditions of friction are: (1) two objects must contact each other 2) There is a squeeze between two objects 3) There is a tendency of motion or relative motion between two objects
1. When an object is stationary on a horizontal plane, if it is not pushed or pulled, it will not be affected by friction. If thrust or pull is received, it belongs to the category of static friction. The size of friction is equal to that of pull or thrust, and has nothing to do with the gravity or pressure of the object. Only the maximum static friction is related to the pressure or gravity on the object
2. If the object is pressed against the wall, the friction force is equal to the gravity of the object
3. As long as the object moves in a straight line at a constant speed on the horizontal plane, the object is subject to the action of balance force in the horizontal direction, that is, the thrust or pull force is equal to the friction force
4. If the object is not pushed by a force of 10N, the object is subjected to static friction, which is equal to the thrust. Just push with 15N force, and the friction force on the object is the maximum static friction force. If the thrust force is increased later, the friction force will not change. Theoretically, the sliding friction of objects is less than the maximum static friction, but it is generally considered that they are equal
5. Pull a 10N object with 15N force to move vertically and uniformly, then the friction force is f = 15-10 = 5N
if you understand my answer above, I think you will have a better understanding of friction force!
the so-called friction is the force that hinders the relative motion of an object, and the direction of friction is opposite to the motion direction or relative motion direction of the object
the conditions of friction are: (1) two objects must contact each other 2) There is a squeeze between two objects 3) There is a tendency of motion or relative motion between two objects
1. When an object is stationary on a horizontal plane, if it is not pushed or pulled, it will not be affected by friction. If thrust or pull is received, it belongs to the category of static friction. The size of friction is equal to that of pull or thrust, and has nothing to do with the gravity or pressure of the object. Only the maximum static friction is related to the pressure or gravity on the object
2. If the object is pressed against the wall, the friction force is equal to the gravity of the object
3. As long as the object moves in a straight line at a constant speed on the horizontal plane, the object is subject to the action of balance force in the horizontal direction, that is, the thrust or pull force is equal to the friction force
4. If the object is not pushed by a force of 10N, the object is subjected to static friction, which is equal to the thrust. Just push with 15N force, and the friction force on the object is the maximum static friction force. If the thrust force is increased later, the friction force will not change. Theoretically, the sliding friction of objects is less than the maximum static friction, but it is generally considered that they are equal
5. Pull a 10N object with 15N force to move vertically and uniformly, then the friction force is f = 15-10 = 5N
if you understand my answer above, I think you will have a better understanding of friction force!
4. 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 movement 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 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 movement 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 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.
5. According to Newton's second law, the resultant force is equal to the mass times the acceleration
6. The friction force is equal to the traction force under the uniform linear motion, which is obtained according to the formula of the balance of the two forces.
7. Child, friction is not created out of thin air. It doesn't mean that as long as an object has friction. For example, if you stand on a level ground, there will be no friction. Friction refers to the force that hinders the relative motion of two objects when they are in relative motion or have the trend of relative motion. It is not a single object, but the force between two objects. For example, when using the rubber, there is friction between the rubber and the paper. If you push a big stone in the horizontal direction, but you don't push it, that's the friction against you. The friction force is related to the pressure and roughness of the contact surface, but not to the gravity
friction factor refers to the ratio of the friction between two surfaces to the vertical force acting on one surface. It is related to the surface roughness, but has nothing to do with the size of the contact area. According to the nature of motion, it can be divided into dynamic friction coefficient and static friction coefficient
I wish you progress in your study!!
friction factor refers to the ratio of the friction between two surfaces to the vertical force acting on one surface. It is related to the surface roughness, but has nothing to do with the size of the contact area. According to the nature of motion, it can be divided into dynamic friction coefficient and static friction coefficient
I wish you progress in your study!!
8. If the computer is not good at drawing, just explain it.
Object B is relatively static with a, so it is subject to static friction here (it is impossible not to be subject to friction force, because there is a relative motion trend between ab). Set f
because ab is relatively static, the acceleration of both is the same, and because it is relatively static, it can be regarded as the same object, and the acceleration A1 = GSIN θ-μ 2gcos θ
now let's look at ab separately. The acceleration of B is A2 = A1 = (mgsin θ- f)/m=gsin θ-μ 2gcos θ,
we can get F= μ 2mgcos θ
Object B is relatively static with a, so it is subject to static friction here (it is impossible not to be subject to friction force, because there is a relative motion trend between ab). Set f
because ab is relatively static, the acceleration of both is the same, and because it is relatively static, it can be regarded as the same object, and the acceleration A1 = GSIN θ-μ 2gcos θ
now let's look at ab separately. The acceleration of B is A2 = A1 = (mgsin θ- f)/m=gsin θ-μ 2gcos θ,
we can get F= μ 2mgcos θ
9. At this time, the car is subject to two pairs of balance forces: a pair of gravity and support force, a pair of friction and thrust
according to the equilibrium condition of the two forces,
the supporting force is equal to gravity, that is, t = g = mg = 50kg × 10N/kg=500N;
friction is equal to thrust, i.e. f = f = 100N
according to the equilibrium condition of the two forces,
the supporting force is equal to gravity, that is, t = g = mg = 50kg × 10N/kg=500N;
friction is equal to thrust, i.e. f = f = 100N
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