An object is acted upon by three common forces that can keep the object in equilibrium

I choose AD. If the three forces reach equilibrium, the sum of the forces is equal to the third force. But force is a vector quantity with magnitude and direction, so it should be calculated according to the addition and subtraction of the vector.

There is no need to calculate this problem, because if a peaceful state can be achieved, it is certain that three forces can be put into a triangle. Then the triangle has a feature that the sum of the two sides is greater than the third side, then analyze the four options, only the magnitude relationship between the three forces in the two options A and D conforms to this characteristic of the triangle, so choose AD.

Because the knowledge has been laid down for too long, some of the expressions are unprofessional and unclear. Thank you for your understanding. If there is anything wrong, I hope my friends will correct it.

That is, the three forces can form a triangle, that is, the sum of the two forces is greater than the third force. ad

a, d of two smaller forces and must = maximum force for the object to balance.

According to the relationship between the side lengths of the triangle, the sum of the lengths of the two sides is greater than that of the third side, and the difference between the lengths of the two sides is smaller than that of the third side.

Choosing A, it seems that there is a parallelogram rule, and the rules for the roots to form triangular rows are similar, the sum of the two sides is greater than the third side, and the difference between the two sides is less than the third side.

AD uses the "triangle method" to easily come up with the answer.

The sum of any two forces greater than the third force may satisfy the condition.

a d both. The sum of any two of the three forces is greater than the third force.

No, to keep an object in equilibrium, it is only necessary that the net force acting on the object is zero years old, but it is not necessarily a common point force. For example, if a long wooden stick is applied to each end of a vertical upward force, the wooden stick is in equilibrium, and the three forces (gravity and two vertical upward forces) on the wooden stick are not at the same point.

If the object is in equilibrium under the action of three forces, then the three forces are not parallel and are at the same point. But under the action of multiple forces, it is not necessarily a block.

The two forces of interaction between the virtual grandchildren of the object (the source can) are balanced, because :

The action force and the reaction force occur at the same time, acting on the same straightness line, equal in magnitude, and in opposite directions.

Therefore they are a pair of equilibrium forces).

The so-called equilibrium is divided into two types, namely fixed-point equilibrium and moment equilibrium.

Fixed-point equilibrium is that all forces can be considered to act on the center of gravity of the object, and then the parallelogram is balanced by forces, which is a kind of equilibrium.

Moment balance requires the sum of the moments of the object to be zero (otherwise rotates and is unbalanced), and the moment is the knowledge of junior high school, which is not much involved in high school. It is enough just to understand the degree.

Moment is the opportunity of force and distance, 9, must be a common point force, common point refers to the reverse extension line of the force is intersected at the same point, 2, can be compared to the magnitude and direction.

The three forces are not necessarily common point forces, 2, the balance of an object is divided into force balance and moment balance. In order for an object to reach a state of stationary or uniform linear motion, it must meet both force balance and moment balance.

For example, the warped version hovering in mid-air, the middle fulcrum supports the upward force, and the two sides are downward forces, no matter which point is taken as the fulcrum, it can be seen that it is the moment vector sum of 0

Addendum: What you mentioned in the supplement is a typical moment balance. 1, not necessarily, imagine that two horses pull a car, but do not pull, the force of the two horses is on both sides, and the friction force is in the middle, not at the same point, 1, an object is in equilibrium under the action of three forces, then these three forces must be common point forces.

If two parallel forces of magnitude 5n and 10n are acting on the object at the same time, but obviously the three of them are not common point forces, but at this time, can it be said that the three forces are in equilibrium?

Equilibrium forces are two forces acting on the same object. If these two forces are equal in magnitude, opposite in direction and in the same straight line, they are called equilibrium forces. Because the effect they produce is negated.

An object exerts a force on two objects at the same time, if the two forces are equal in magnitude and in opposite directions and in the same straight line, but their effects are on different objects and cannot be cancelled out, but the reaction force of these two forces acts on the same object. They're a balancing force.

Equilibrant. Forces acting on an object can be of different natures – such as gravity and the tension (elastic force) of a rope that is straight upwards – these two forces are of different natures;

The mutual force acting on different old objects is a force of the same nature - the pressure of the object on the flat surface and the support force of the object on the plane - they are both elastic forces and have the same nature!

Hello! According to the triangle principle, the range of the resultant force that can be produced by two forces is f1-f2<=f<=f1+f2

Therefore, in b, the resultant force that can be produced by 1n and 3n is in the range of 2n to 4n. It is impossible to balance with 5n thank you!

Answer: If the three common point forces of ad want to make the object in a state of equilibrium, then take the magnitude of these three forces as the edge, and form a closed triangle, and the minimum value of the net force is zero. Such as: item a:

The resultant force of 5n and 7n ranges between 2n and 12n, and the third force 8n is in the range, so the minimum value of the resultant force is 0n, which can put the object in equilibrium, and the term a is correct; The same can be judged that the D top is correct.

The effect of force is that the force can change the state of motion of the object, if an object is only in equilibrium under the action of two forces, then these two forces are a pair of balanced forces, and the effect of these two forces cancels each other out, that is to say, the effect of these two forces cannot be expressed, so the state of motion of the object must remain unchanged.

The point is that the state of movement does not change, and what is the change of state of movement. There are three types of motor state changes:1

The velocity of the object changes by magnitude, 2The direction of motion of the object changes. 3.

The direction of motion and the magnitude of the velocity of the object change.

If the state of motion does not change, it only includes the state of rest and the state of uniform linear motion.

When an object changes from rest to motion, it is in a non-equilibrium state, and it must be affected by an unbalanced force. When the object becomes in a uniform linear motion, it is in equilibrium.

Rest is a state of equilibrium, uniform linear motion is another equilibrium state, from rest to uniform linear motion is from one equilibrium state to another, in the process of course the state of motion is changing.

Because force is the cause of changing the state of motion of an object, it will not change the state of motion as long as the force is balanced.

And stationary and uniform linear motion are two different states of motion, so it takes a little force to change from stationary to uniform linear motion, but when entering uniform linear motion, there is a state of equilibrium of two forces.