A formula for calculating support force

1.

1. Gravity g = mg

(vertically downward, g = 9.8m/s2 ≈ 10m / S2, the action point is at the center of gravity, applicable to the earth surface)

2. Hooke's law f = KX

{along the recovery deformation direction, K: stiffness coefficient (n / M), X: deformation variable (m)}

3. Sliding friction force F = μ FN

{opposite to the relative motion direction of the object, μ： Friction coefficient, FN: positive pressure (n)}

{rrrrrrr}

extended data:

different classification of force

1. According to the nature of force, it can be divided into gravity, universal gravitation, elastic force, friction force, molecular force, electromagnetic force, nuclear force, etc Note that gravity is not equal to gravity under all conditions Gravity does not point to the center of the earth under all conditions. Gravity is a component of the earth's gravitational force on an object, and the other component is a centripetal force. Only on the equator does gravity point to the center of the earth.)

According to the effect of force, it can be divided into tension, tension, pressure, supporting force, power, resistance, centripetal force, restoring force, etc

According to the research object, it can be divided into external force and internal force

According to the action mode of force, it can be divided into non-contact force (such as gravitation, electromagnetic force, etc.) and contact force (such as elastic force, friction force, etc.)

There are four basic interactions (forces): gravitational interaction, electromagnetic interaction, strong interaction and weak interaction

nature of force:

materiality: force is the effect of an object (matter, mass) on an object (matter, mass). When an object is subjected to a force, another object must exert this effect on it. Force cannot exist independently without an object

interactivity (interaction): the interaction between any two objects is always mutual, and the object exerting the force must also be the object under the force. As long as one body exerts a force on another, the stressed body in turn will surely add a force to the exerted body Generating conditions: the force is equal in size (the resultant force is zero, in a state of non directional static motion) or not equal, in the opposite direction, acting on two different objects, and acting on the same straight line. It can be summarized as: foreign body, equivalent, reverse, collinear. A pair of interaction forces must proce and disappear at the same time.)

Vectoriality: force is a vector, which has both magnitude and direction

simultaneity: the force proced and disappeared at the same time

independence: the effect of one force does not affect the effect of another

includes three elements: the size, direction and action point of the force. The accurate expression of the three elements of force by a directed line segment is called the diagram of force. The size is represented by the length of a scaled line segment, the direction is represented by an arrow, the point of action is represented by an arrow or the tail of an arrow, and the straight line along which the direction of a force follows is called the line of action of a force. The diagram of the force is used for the calculation of the force. When the judgment power is large, we must pay attention to the scale of the line segment, because even if one line segment is longer than another line segment, but the scale of the long line segment is also longer, the force represented by the short line segment is not necessarily smaller than that represented by the long line segment

2.

There is no specific formula for supporting force. Sometimes supporting force = gravity or = friction

when expounding the concept of supporting force, it is always said that one object has supporting force for another, then the latter is the stressed object, and the point of action should be marked on the stressed surface. For example, if a wooden block is placed on the horizontal desktop and is supported by the desktop, the point of action of the supporting force is marked on the center of gravity of the wooden block

{rrrrrrr}

extended data:

I. nature of force:

1. Materiality: force is the effect of object (matter, mass) on object (matter, mass). When an object is under the action of force, another object must exert this effect on it. Force cannot exist independently without object

3. Vectoriality: force is a vector, which has both magnitude and direction

4. Simultaneity: the force proced and disappeared at the same time

Independence: the effect of one force does not affect the effect of another

According to the nature of force, it can be divided into gravity, universal gravitation, elastic force, friction force, molecular force, electromagnetic force, nuclear force, etc. Gravity does not point to the center of the earth

2. According to the effect of force, it can be divided into tension, tension, pressure, supporting force, power, resistance, centripetal force, restoring force, etc< According to the research object, it can be divided into external force and internal force

4. According to the action mode of force, it can be divided into non-contact force (such as gravitational force, electromagnetic force, etc.) and contact force

5. Four basic interactions (forces): gravitational interaction, electromagnetic interaction, strong interaction and weak interaction

3. The weight only increases the gravitational potential energy, as long as the height change is calculated
two right triangles can be made from two positions AB, and the bottom length of the two triangles can be expressed by height H. the difference between them is 2, and the height h can be solved. Then the oblique side length of the two triangles can be calculated respectively, and the difference is the change of height.

4.

F = UN (U is the dynamic friction coefficient)

resistance can be divided into many kinds of resistance. The calculation formula of air resistance FW is: FW = 1 / 16 · a · CW · V2 (kg), V is the driving speed, unit: M / s, a is the cross-sectional area of the vehicle, unit: M2: CW is the wind resistance coefficient

When the fluid flows in the pipe, the flow resistance will be increased e to the local obstruction of pipe fittings and valves, as well as the resistance caused by the expansion or rection of the flow section

extended data:

precautions:

1. Arm of force refers to the distance from the fulcrum to the action line of force (power or resistance), not from the fulcrum to the action point of force

When the direction of the force acting on the lever changes, the size of the force arm will also change

The arm of force is not necessarily on the lever

If the action line of the force passes through the fulcrum, the arm of force is zero

There are three steps to draw the force arm: find the fulcrum, draw the action line of the force, and draw the vertical line from the fulcrum to the action line of the force (sometimes it is necessary to extend the action line of the force in the forward or reverse direction)

5. Drawing on the contact surface is the most correct, but generally the object is regarded as a particle ~ ~ so you are right to draw on the center, which is more intuitive and easy to calculate

6.

The object is balanced in the vertical and inclined directions: the supporting force n = mgcos α.

But there is a problem in the calculation of impulse of support force N: according to the definition of impulse, f * T = Δ MV, where F * t Δ M V are all vectors -- & gt; F * T and Δ M V directions must be collinear. The supporting ability of the question n = mgcos α Perpendicular to the slope -- & gt; Support force n has no impulse to object motion

7. Remember, the support force is f, the mass is m,
f-mg = ma, and a is the acceleration of a person moving up or down (up is + and down is - 0 at rest). According to this formula, we can calculate F
the above is limited to the vertical direction

If a person is still on the inclined plane, the supporting force of the inclined plane to the person is f = mg * cos α，α Is the inclination of the slope).

8. The specific situation should be analyzed in detail! Holding force = gravity, or = friction, or = gravity friction

9. Work is the proct of force and displacement in the direction of force. The displacement in the direction of force is the displacement of the action point in the direction of force
if the supporting force has displacement in the direction, then the supporting force does work and can be substituted into the formula! If the point of action of supporting force does not change, no work will be done!

10. When a body is moving in a straight line at a constant speed, traction is equal to resistance, because traction and resistance are a pair of balanced forces