How to calculate the friction force of uniform linear motion
Publish: 2021-04-27 11:39:05
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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. (1) If the object moves in a straight line at a constant speed on a horizontal plane, so the pulling force and friction force are balanced, then f = f = 20n< (2) the sliding friction is related to the pressure and the roughness of the contact surface, but has nothing to do with the speed
(2) when an object moves in a straight line at a speed of 2 m / s, the friction force is constant; Because the sliding friction is related to the pressure and the roughness of the contact surface, but not to the speed
(2) when an object moves in a straight line at a speed of 2 m / s, the friction force is constant; Because the sliding friction is related to the pressure and the roughness of the contact surface, but not to the speed
4. In the real world, uniform linear motion is only an ideal form of motion. In practical application, we use the formula v = s / T, s = VT to deal with the problem, Its essence is that most of the variable speed motion is approximately regarded as uniform motion.
the dynamic friction factor is determined by the material of the contact surface and the roughness of the contact surface, and has nothing to do with the pressure between two objects and whether relative sliding occurs
the question is friction coefficient, and their answers are all about whether the friction will be 0
the dynamic friction factor is determined by the material of the contact surface and the roughness of the contact surface, and has nothing to do with the pressure between two objects and whether relative sliding occurs
the question is friction coefficient, and their answers are all about whether the friction will be 0
5. Yes, because it's in uniform motion
6. First question: the two forces are balanced, and the friction force is also 10N
second question: 10N, because the friction force is only related to the pressure and the roughness of the contact surface. If these two conditions remain unchanged, the friction force also remains unchanged. When the tension force is 30n, the object will accelerate.
second question: 10N, because the friction force is only related to the pressure and the roughness of the contact surface. If these two conditions remain unchanged, the friction force also remains unchanged. When the tension force is 30n, the object will accelerate.
7. Let the mass of the object be m and the angle between the conveyor belt and the horizontal plane be m θ, The object on the conveyor belt is affected by the supporting force N, gravity (g = mg) and friction F. the component of gravity along the inclined plane (conveyor belt) is mgsin θ. According to Newton's second law,
when the conveyor belt moves upward with constant speed and linear acceleration a,
f-mgsin θ= Ma... (1)
when the conveyor belt moves downward in a straight line with constant speed and acceleration a,
mgsin θ- F = ma... (2)
so:
when the conveyor belt moves upward with constant speed and linear acceleration a,
from (1), the friction force can be calculated as F = m (a + GSIN) θ.
when the conveyor belt moves downward in a straight line with constant speed and acceleration a,
from (2), the friction force can be calculated as F = m (GSIN) θ- a)
when the conveyor belt is moving in a straight line at a uniform speed, no matter upward or downward,
the friction force can be calculated as F = mgsin by (1) or (2) making a = 0 θ.
when the conveyor belt moves upward with constant speed and linear acceleration a,
f-mgsin θ= Ma... (1)
when the conveyor belt moves downward in a straight line with constant speed and acceleration a,
mgsin θ- F = ma... (2)
so:
when the conveyor belt moves upward with constant speed and linear acceleration a,
from (1), the friction force can be calculated as F = m (a + GSIN) θ.
when the conveyor belt moves downward in a straight line with constant speed and acceleration a,
from (2), the friction force can be calculated as F = m (GSIN) θ- a)
when the conveyor belt is moving in a straight line at a uniform speed, no matter upward or downward,
the friction force can be calculated as F = mgsin by (1) or (2) making a = 0 θ.
8. It's not equal to, the sliding friction is equal to the friction coefficient u times the supporting force of the ground
when an object moves horizontally and uniformly, if there is no other force, the friction is equal to UMG
welcome to ask~
when an object moves horizontally and uniformly, if there is no other force, the friction is equal to UMG
welcome to ask~
9. If it is a relative motion, it is only related to the pressure and sliding friction coefficient between objects, f = n μ， It has nothing to do with velocity and acceleration.
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