Is it true that mechanical energy is conserved when an object is acted upon by only one pair of equ

Not right for any student of intellectual level.

If the object moves at a uniform speed on a rough surface under tension f the frictional force f = f the object is still in equilibrium but the mechanical energy is converted into internal energy.

It would be correct to add rest before the object in the question.

Falling at a constant speed is in equilibrium, but it still can't refute the idea that friction can still be ruled out in the falling process.

As long as there is friction, there is mechanical energy converted into internal energy, and mechanical energy is not conserved, but total energy is conserved.

This sentence only emphasizes the balance of forces There are two conditions for the conservation of mechanical energy Force balance Mechanical energy is not converted into other forms of energy Junior high school students only need to consider whether there is friction or not whether the force is balanced or not.

No, for example, if the tensile force f and the friction force f are equal and reversed, then isn't it balanced? However, friction generates heat, and there is bound to be a loss of mechanical energy.

Is this sentence true or false for junior high school knowledge!!

Another "Is falling at a constant speed a balancing force?" Can this sentence refute this view?

Yes, falling at a uniform speed is the action of the equilibrium force. This sentence can refute the point of view because mechanical energy has kinetic energy and potential energy. The kinetic energy does not change, the gravitational potential energy decreases, and the mechanical energy is bound to be not conserved.

No, mechanical energy includes gravitational potential energy and kinetic energy, and at this time, the kinetic energy does not change, and there is no guarantee that the gravitational potential energy will also remain unchanged.

The object falls at a constant speed, the kinetic energy does not change, the gravitational potential energy decreases, and the mechanical energy decreases. The condition for the conservation of mechanical energy is the condition that the work is done without external force or only gravity.

Bu right, the kinetic energy does not change, and the gravitational potential energy can change.

No, for example, if you push a person and an object to slide at a uniform speed on a rough horizontal plane with your hands, the thrust and friction force are a pair of balancing forces. But friction heats up, indicating that there is mechanical energy converted into internal energy.

That's right. When the equilibrium force is acted, the resultant external force is zero, which can be regarded as not being affected by the external force. Conservation of mechanical energy.

Not true. Conservation of mechanical energy is the law of conservation of energy. Equilibrium is simply a relative balance that moves at a uniform speed.

No, such as falling at a constant speed.

The basic formula for rigid body mechanics is l=jw.

Data Extension:

Rigid body mechanics is a discipline that studies the laws of motion (including rest) of rigid bodies under stress. According to the different states of motion, it can be divided into rigid body dynamics, rigid body statics, and particle mechanics to study the motion of the particle. m=ja;The relationship between angular acceleration and the magnitude of the force is revealed.

When the line between the point of action of the impulse (force) and the center of mass is the direction of the force, this situation is the simplest, that is, it moves in a straight line and does not rotate.

When the connection line and the direction of impulse are different, it can be solved by using the three equations of conservation of mechanical energy + conservation of momentum + conservation of angular momentum, which is relatively simple (depending on whether the data is good or not, there are more unknown quantities here, I will not write the punch in detail, the format is very troublesome). It gives you a rough model of the object moving in the direction of p, but at the same time rotating around its own center of mass.

Translation: During the movement of a rigid body, the lines of any two points on it remain parallel at all times. (There is nothing to say about translation, you can use Sanjian Town as a particle to calculate, basically everyone can use the knowledge learned in high school to complete the calculation of translation).

Rotation: All particles on a rigid body move in a circular motion around the same straight line. This motion is called the rotation of a rigid body. This straight line is called the pivot. (This part is the focus of rigid body mechanics, and the following part is about the rotating part of rigid bodies).

Mechanical energy: Gravitational potential energy, elastic potential energy, and kinetic energy are collectively referred to as mechanical energy.

Only when gravity (or spring force) does work, the gravitational potential energy (or elastic potential energy) and kinetic energy of the object are converted into each other, but the total mechanical energy remains the same.

Conditions for conservation of mechanical energy:

1) If an object is only affected by gravity, the mechanical energy of the system composed of the object and the earth is conserved.

2) For an object to be acted on by other forces in addition to gravity, but only gravity does work, and other forces do not do work, then the mechanical energy of the system composed of the object and the earth is conserved.

3) If an object is subjected to several forces, only the spring elastic force does the work, and the other forces do not do the work, then the mechanical energy of the system composed of the object and the spring is conserved.

4) If an object is subjected to several forces, only gravity and spring force do the work, and the other forces do not do the work, then the mechanical energy of the system composed of the object, the spring and the earth is conserved.

The external force of the object under the action of the equilibrium force is zero and does not meet the above conditions. Only the object moving under the action of gravity depends on whether other forces do work and song, if an object is affected by other forces in addition to gravity, but only gravity does infiltration work, and other forces do not do work, then the mechanical energy of the system composed of the object and the earth is conserved, otherwise it is not conserved.

Not conserved. Conservation of mechanical energy.

Condition: Only gravity (elastic force) does high work on the object.

At. Equilibrant.

As used by Nian Feng, not only the gravity dregs (elastic force) do the work, but also balance with the gravity (elastic force). The force also does the work.

When an object is subjected to a balanced force, it is in equilibrium; There are two types of equilibrium states: the state of rest and the state of uniform linear motion

When the object is at rest, the kinetic energy and potential energy of the object are unchanged, so the mechanical energy is also unchanged;

When an object moves in a uniform linear motion in the horizontal direction, its kinetic energy and potential energy remain unchanged, that is, the mechanical energy remains unchanged;

When an object moves in a uniform linear motion in the vertical direction, its kinetic energy does not change, but its potential energy changes, so the mechanical energy also changes

In short, there are two possibilities for the magnitude of potential energy and mechanical energy in the above possible states of motion: unchanged or changing; So A is correct, CD is wrong;

And kinetic energy has only one case: it does not change; Therefore B is wrong

Therefore, a

Judge the change of an object after being subjected to force from a common phenomenon in daily life.

Answer: B

Analysis: The object is affected by the equilibrium force and will be stationary or do uniform linear motion.

When the object is at rest, the potential energy does not change;

But when the object is moving in a uniform linear velocity, the velocity is the same, and the kinetic energy is the same, but when it is moving in a uniform linear velocity, it can also be completely upward or downward, and if the downward velocity is uniform, the potential energy is reduced. The kinetic energy is constant regardless of whether the velocity is 0 or the velocity is constant.

So AD is wrong. The potential energy decreases, the kinetic energy does not change, and the mechanical energy decreases; If the upward velocity is uniform, then the potential energy increases, the kinetic energy does not change, and the mechanical energy increases.

The answer is c. Because when an object is subjected to a pair of equilibrium forces, the object is in equilibrium, either at rest or in a straight line at a uniform speed, it is judged that if the object is originally in motion, its velocity remains the same, and therefore the kinetic energy is constant.

An object is acted upon by two forces and remains at rest or in a state of uniform linear motion, and these two forces are a pair of balanced forces, which is called two-force equilibrium.

b: When the kinetic energy is unchanged when the constant speed plummets, and the potential energy decreases, the mechanical energy decreases.

C: The kinetic energy must not change.

So the answer is b.

When an object receives a pair of equilibrium forces, is it incorrect to judge its state and changes? b。Gravitational potential energy may increase blindness. Thank.

Huh. Choose C

When the object is subject to a pair of equilibrium forces.

The object is either moving in a straight line at a uniform speed.

Either stand still.

Option a. If the object moves downward at a constant speed.

Its gravitational potential energy decreases, and the kinetic fiber energy remains unchanged.

Option b. If the object moves upwards at a constant speed.

Its gravitational potential energy increases.

The kinetic energy becomes smaller. c option.

When an object is subjected to a pair of equilibrium forces.

Uniform linear motion.

So the speed remains the same.

And the quality remains the same as the first lease.

So the kinetic energy remains the same.

d option. If the object moves in a straight line at a uniform speed in the horizontal direction.

Then both the gravitational potential energy and the kinetic energy are constant. Old. Choose C

The object is under the action of a balanced force:

When the object rises, the mechanical energy increases.

When the object descends, the mechanical energy decreases.

When the object moves horizontally, the mechanical energy does not change.

When the object is at rest, the mechanical energy does not change.

dAll three of the above are possible.

For example, if a rope pulls an object up at a constant speed, the mechanical energy of the object increases. When the velocity decreases, the mechanical energy decreases.

Equilibrium can only ensure that the kinetic energy remains unchanged, but cannot guarantee the change of potential energy.