The two forces of mutual action and reaction force one does work, and the other must do work

Not necessarily, for example, in a magnetic field, the fixed magnet A pushes away magnet B, A does work on B's force, and B does not work on A's force (no displacement).

Not necessarily, you push the box, the box doesn't necessarily push you.

1. The work done by a pair of interaction forces is the work of a pair of equal and opposite forces acting on two objects respectively.

2. The interaction force is one of the natural fundamental forces of the universe, and the condition for its establishment is that as long as an object exerts a force on another object, the stressed object will in turn definitely exert a force on the object applying the force. It is simply summarized as the same application point, equivalence, inverse, and collinear. A pair of interacting forces must arise and disappear at the same time.

This statement is false. Since the action and reaction forces are "simultaneous", they must act for the same time. For example, the spring is compressed with a thin wire in the middle of the two trolleys, placed on a smooth horizontal plane, and the thin wire is sheared, and the force of the spring on the two trolleys is positive, and the kinetic energy of the trolley increases.

Therefore, it is wrong to say that when the force does positive work, the reaction force must do negative work.

The law of action and reaction is further divided into two versions: strong and weak. Here, the third law states the "law of weak action and reaction".

The "law of strong action and reaction", in addition to the law of weak action and reaction, also requires that both action and reaction act in the same straight line. Both gravitation and electrostatic forces obey the law of strong action and reaction. However, in some cases, the action and reaction forces are not in the same line (the line connecting the two points of action).

For example, two electric charges in translational motion have the same translational velocity, but are not perpendicular to the line connecting the two charges, and the action and reaction forces calculated by the Biot-Chavar point charge law and Lorentz force law are not in the same line. This force only obeys the law of weak action and reaction. For example, if two electric charges moving in translational motion are moving perpendicular to each other, the electromagnetic force they each feel does not obey the law of weak action and reaction.

This is a very interesting question.

According to Newton's third law, the action and reaction forces must always be equal in magnitude and opposite directions, acting on the same straight line. Therefore, the work done by each of the two forces must also be equal in magnitude and opposite in direction. That is, the combined work must be zero.

However, it is important to note that the action and reaction forces described by Newton's third law act on two different objects. The force exerted by object A on the force f of object B must cause object B to react to object A with a force -f. That is, the force applied is to object B, and the reaction force is applied to object A.

Therefore, the original meaning that the action of two objects is 0 is another representation of the conservation of energy.

That is, the energy increased by object B under the action of object A is equal to the energy lost by object A by the reaction of object B.

Yes, the acting force and the reaction force are of the same magnitude and opposite directions, and the total work done must be 0

The work done by friction (including static friction) depends on the relative displacement, and the sum of the work done under positive pressure is zero.

Is the sum of the work done by the action and reaction always equal to zero – not necessarily!

The force acting is the reaction force.

Acts on two objects. For example, if one moves in the direction of the force, then the force does work, but if the other object of the reaction force is still stationary, then the reaction force obviously does not work on this object or the work done is zero, then the sum of the two is not zero.

For example, if an object slides on the ground, the force is the frictional force of the ground against the object, which does negative work and is not zero.

Whereas, the reaction force is the frictional force of the object against the ground, while the ground is stationary, so the reaction force does not do work. The sum of the two is not zero.

Wrong. The work done by the action force has nothing to do with the work done by the reaction force.

That is to say: 1. The action force and reaction force can be done by one to do positive work and the other to do negative work.

For example, the car pulls the wooden box to accelerate forward, and the car and the box remain relatively stationary. This is the positive work of the friction of the car on the wooden box, and the negative work of the friction of the wooden box on the car.

2. Both the action force and the reaction force can do negative work.

3. The action force and reaction force can both do positive work.

4. The action force and reaction force can be one to do work, and the other can not do work.

Correct answer: c

a。When positive work is done with force, the reaction force must do negative work. ......False, the force of action and reaction force are two, not two forces of one object, although they are in opposite directions, but the two objects may also be in opposite directions, both do positive work.

For example, if two people push each other and both people are bounced off, the action and reaction force in this process do positive work.

b。When no work is done with force, no work is done by the reaction force. ......Correct, c. When the action force does positive work, the reaction force can also do positive work ......Wrong, two people in the car pushed each other, one positive and one negative.

d。The work done by the action force and the reaction force must be equal in magnitude and opposite in positive and negative ways. ......Wrong, if the two masses are not the same, the displacement will be different, and the work done will be different; The direction may also be different.

2.Functional relationship, work done by a person on an object = kinetic energy of an object.

w=3.The constant power process is not uniformly accelerated, and formulas such as v=at cannot be used.

As S increases, the acceleration a decreases, and the acceleration is 0 at a constant velocity The specific formula cannot be found, and the integral is involved.

4.Because it happens to be able to slide down at a constant speed, the amount of potential energy change = the amount of work done by friction.

Ascending process: Reduction of mechanical energy = friction doing negative work e= ep

5.The horizontal force does the positive work first, then the positive work, the work done and the amount of change for the kinetic energy of the object. ∴w=0

Brother, I don't have time to come up and make up the score.

Answer: D solution: The action force and the reaction force must be equal in magnitude and opposite directions.

But to consider doing work, one also needs to know the displacement of the force. When doing positive work, the displacement of the reaction force is unknown and uncertain.

For example, if I pull this object towards 1 object so that it is close to me, my pulling force is doing positive work. For this pull, the reaction force is the pull force of the object against me.

If I also move 1 point away from the object while pulling (e.g. when the ground is too slippery, you pull the trolley with a rope, you will have a displacement towards the trolley. ), then the reaction force is in the same direction as the displacement, and the positive work is done;

If I stand still, then the reaction force has no displacement, and the work done by the reaction force is 0;

Suppose I walk 1 point in the opposite direction of the object while pulling (for example, if I pull the car forward, I am walking in the opposite direction of the car). Then the reaction force and the displacement are in opposite directions, doing negative work.

Only d pairs.

Work = force * displacement (to ground) in the direction of the force.

Force and reaction force act on two different objects respectively, to see whether these two forces do work, whether they are positive or negative work, it depends on whether the two objects (to the ground) have displacement.

For example, two small balls with positive and negative charges respectively A and B are fixed on a smooth insulating horizontal plane and are separated by l, if only B balls are released, B will approach A because the charges attract each other. In this case, only the force (gravitational force) received by B does positive work, while the reaction force (gravitational force) received by A does not do work.

This example negates the "certain" in a, b, and c in the title

In this example, if two balls are released at the same time, both gravitational forces work positively.

So, d is right, right is "okay".

Choose the D formula: The action force and the reaction force are just the same magnitude and the direction is opposite, but it doesn't matter in the work! Don't be fooled...

For example, the stove is illustrated: on the smooth horizontal plane, there is a compressed spring between the two sliders that is locked, and after the locking is released, the spring is elongated, and the two sliders are doing positive work. The elastic force of the spring is understood as a pair of mutually hidden forces between the two sliders, that is, the force of the slider 1 on the slider 2 through the spring and the force of the slider 2 on the slider 1 through the spring.

So this conclusion is correct. Generally speaking, there are various possibilities for the work done by the action force and the reaction force. Envy replied.