18 Under the action of a common point force, the equilibrium condition of the object is zero resulta

Yes, no matter how many forces an object is subjected to, and regardless of the direction of those forces, as long as the net force of these forces is zero, the object must be in equilibrium (stationary or uniform linear motion).

The point is that you have to understand what the resultant force is, and the so-called resultant force does not mean that the object is subjected to another force, but that if the object is subjected to several forces and produces the same effect as the object is subjected to only one force, then this force can be called the resultant force of those forces.

In other words, if the net force on the object is zero, it means that no matter how many forces the object is actually subjected to, as long as the net force of these forces is zero, it is equivalent to a force that is not applied at all (as long as the net force of these forces is zero, the effect of these forces on the object is the same as if the object was not acted on by any external force), and then according to Newton's first law, it can be known that the object remains at rest or in a uniform linear motion (i.e., equilibrium) without any external force

That's right. This is because whether or not the state of motion of an object changes depends on the net force to which the object is subjected.

According to the plane convergence equilibrium force system of statics, the equilibrium condition is zero resultant force, and the equilibrium condition is still applicable in the spatial state.

Under the action of the common point force, the equilibrium condition of the object is zero resultant force. Right.

An object is subjected to two common point forces, regardless of the situation, and its resultant force ().

a.It must be greater than any one of the components.

b.To Tongbi less than a component.

c.It is not greater than the sum of the size of the two components, and it is not less than the difference between the size of the two components.

d.It increases with the increase of the angle between the two components.

Correct answer: not greater than the sum of the magnitude of the two components, not less than the difference between the magnitude of the two components.

First of all, understand what is called a state of equilibrium!

The equilibrium state means that the state of motion of the object does not change, that is, the object has zero acceleration.

Therefore, the external force must be zero.

Therefore, the conclusion of the question is correct!

I think this question is a test of your understanding of the balanced nature of force. Then the resultant force experienced by the object is zero, and the resultant force must be zero in equilibrium, but the resultant moment is not necessarily zero. So I don't choose it.

When an object is at rest, it doesn't have to be in equilibrium! For example, if an object is thrown vertically to reach the highest point, the velocity is 0

But the resultant force is not 0

Not in equilibrium.

According to Newton's second law, the expression f is combined = ma

The content of the law: The acceleration of an object is proportional to the resultant force f exerted on the object, inversely proportional to the mass of the object, and the direction of acceleration is the same as the direction of the resultant external force.

So that's true!

The resultant force is zero.

The resultant moment is not necessarily zero.

If the resultant moment is not zero.

will rotate around itself.

If the resultant moment is a certain value.

It will accelerate to the speed of light and create a black hole.

Can you say that the black hole that devours everything is in equilibrium?

Newton's three laws are clearly problematic.

Why bother to pick out books.

The ancients said that it is better to believe in books than to have no books.

Wrong. For example, if you have a light spring, you pull your left and right hands in opposite directions with a force of 10 n (net force is 0), but the spring continues to elongate (non-rigid body).

On the seesaw, a child weighing 400n sits at one end and you push the seesaw with a force of 400n in the opposite direction, and you will find that the seesaw will send the child to the ground. The seesaw is balanced by the external force, but the external moment is unbalanced!

In a non-inertial frame of reference, such as the Earth, the Earth's gravitational pull from the Sun is balanced by its inertial force (centrifugal force) in the frame of reference, but the Earth orbits the Sun.

Therefore, that sentence must be added with the appropriate conditions to be true:

The condition is a rigid body in an inertial frame, the resultant force is balanced, and the line of action of the force is over the center of force (there is no moment).

In this way, two rods, each with three common point forces, are balanced, and if the two rods are connected together, that is, one rod, will be balanced by these six forces, but the six forces do not extend the line to meet at one point.

Answer: d The object is in equilibrium, it may be at rest or in a uniform linear motion, but the net force must be 0, abc is wrong d right.