How to calculate friction based on gravity
Publish: 2021-04-25 22:16:55
1. 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.)
2. First of all, judge whether it is static friction or sliding friction. Static friction should be formulated according to Newton's second law. If it is in an equilibrium state, it can also be formulated as an equilibrium equation. If it is sliding friction, use f = UN, and remember that it is multiplied by elastic force, which is not necessarily equal to gravity
3. As long as the pressure branch generated by gravity is not zero and the contact surface is not deformed by pressure, the relationship between gravity and friction is proportional.
4. No friction coefficient
you don't know whether you can push or not
F = UMG (friction coefficient when u)
but if you can't push, friction is equal to thrust
pushing friction is equal to UMG
friction is divided into dynamic friction and static friction
if the object doesn't move relative to each other, there is no dynamic friction
dynamic friction f = UMG (U is dynamic friction coefficient 0 < U < 1), which is also the maximum static friction Force
if there is no dynamic friction coefficient, the maximum static friction can not be determined
for your problem,
if the object has relative motion, then the dynamic friction = UMG (regardless of the uniform speed, If there is no relative motion,
then the static friction is always equal to the thrust so that the two forces can be balanced
the above is the theory
let's analyze your problem
the first g = 10
F = 3
because 0 < U < 1
then the maximum static friction in the range of 0 < f < 10N
may be less than f or greater than f
so it is not necessary It can judge whether the object is moving or not
but as you said that even the motion is a straight line with uniform speed
the size of F can definitely be 3N
(force balance)
similar to question 2
3
the maximum static friction must be less than the thrust f
so the object must move
but it cannot be uniform
because the thrust is greater than the friction
so these two questions can judge whether the object can move, But we can't determine the amount of friction
you don't know whether you can push or not
F = UMG (friction coefficient when u)
but if you can't push, friction is equal to thrust
pushing friction is equal to UMG
friction is divided into dynamic friction and static friction
if the object doesn't move relative to each other, there is no dynamic friction
dynamic friction f = UMG (U is dynamic friction coefficient 0 < U < 1), which is also the maximum static friction Force
if there is no dynamic friction coefficient, the maximum static friction can not be determined
for your problem,
if the object has relative motion, then the dynamic friction = UMG (regardless of the uniform speed, If there is no relative motion,
then the static friction is always equal to the thrust so that the two forces can be balanced
the above is the theory
let's analyze your problem
the first g = 10
F = 3
because 0 < U < 1
then the maximum static friction in the range of 0 < f < 10N
may be less than f or greater than f
so it is not necessary It can judge whether the object is moving or not
but as you said that even the motion is a straight line with uniform speed
the size of F can definitely be 3N
(force balance)
similar to question 2
3
the maximum static friction must be less than the thrust f
so the object must move
but it cannot be uniform
because the thrust is greater than the friction
so these two questions can judge whether the object can move, But we can't determine the amount of friction
5. When gravity is the positive pressure, f = MGU, (U is the friction coefficient); When the component of gravity is a positive pressure f=tan@mgu (this formula is not necessarily, but the specific situation is analyzed).
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7. It will take us about twenty minutes to get to the sports center
8. I want to play table tennis in gymnasium.
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