Use the knowledge of the second year of junior high school to answer the question Why does the velo

With gravitational acceleration, the object accelerates towards the center of the earth.

The force is unbalanced when the object falls, and the resultant force is the gravitational force minus the frictional force in the opposite direction. Under normal circumstances, the air friction is relatively small, and the resultant force on the object is downward, and the downward resultant force produces a kinetic energy effect on the object, making it faster. Because the object is always subjected to this resultant force during the fall.

Gu speed is getting faster and faster.

Because he receives the action of gravity, the force will change the motion of the object, so the speed becomes greater.

The object is still subject to gravity in the air, that is, the attraction of the earth to the object, and the velocity of the object changes when it is subjected to external force, and when the object falls, the direction of the fall and the direction of the force are the same, so the velocity of the object becomes greater when it falls.

When an object is not subjected to force, or is subjected to a balanced force, it always remains at rest or moves in a straight line at a uniform speed. Force can change the speed and direction of motion, and in free fall, objects are subjected to gravity. So accelerate the fall.

Because of gravitational attraction, gravitational acceleration.

According to Newton's principle of inertia, an object always maintains a uniform velocity or is at rest when it experiences zero external force.

The external force on which the object falls is the gravitational force of the planet.

As you can imagine, an object that is moving by inertia has a faster velocity than the last time it is subjected to a force (differential).

In the words of the second year of junior high school, ha, then you can't use gravitational acceleration to say, you can understand it like this——— the object falls down under the action of gravity, and then it falls like that, to accelerate and accelerate, and then suddenly its speed does not change, because his mother's gravity can only accelerate like this, only so fast, so it is to first become larger and then reach the maximum, the famous physicist Galileo Galilei once did a world-famous experiment on the Leaning Tower of Pisa, Italy. He dropped two large and small iron balls with great differences in size and mass at the same height, and the result landed at the same time. This experiment disproved Aristotle's theory that the speed of an object falling into the ground was related to its mass.

Of course, modern people have a big ideological misunderstanding, thinking that the object must land first, but it is actually wrong, and the truth of this conclusion can be better reflected in the vacuum. Therefore, the fall of the object is related to gravity and the gravitational acceleration that I didn't learn in junior high school... Does the landlord give a point?

Quite simply, when the object is not affected by force, or when it is balanced by force, it will maintain its original state of motion: either it will keep moving in a straight line at a uniform speed, or it will remain at rest. When the force of the object is unbalanced, it will change its own state of motion, to put it bluntly, it will change its own velocity, when the direction of the force it is subjected to is the same as the original velocity, the velocity increases, otherwise the velocity decreases.

When the object is reduced by gravity, the original velocity is the same as the direction of the force, so its velocity increases...

This issue should be discussed on a case-by-case basis.

1. Under ideal circumstances, if the object has a certain potential difference with the central celestial body, the object will move in the direction of the decreasing potential difference under the gravitational pull of the central celestial body until there is no potential difference, and the two remain relatively stable. The ideal situation we are talking about here is that there is no additional resistance, that is, there is no other external force in the direction of the potential difference, in this case, according to the relevant knowledge of mechanics, the acceleration during the fall is provided by the central celestial body, the closer to the central celestial body, the greater the acceleration, then the falling speed of the object is determined by the acceleration, independent of the mass of the object.

2. If you start from reality, mass is usually combined with volume. On the earth in which we live in reality, there is a certain range of distribution of the density of objects, that is, the density cannot be infinitely large, and it cannot be infinitely small. Then the higher the mass, the larger the volume.

If on the earth and on a planet with a certain atmosphere like Mars, the object will be additionally subjected to air resistance when falling, which is proportional to the square of the falling speed of the object, f=kv, k is a scale factor, which is related to the characteristics of the object itself. Then when the velocity reaches a certain size, there will be a situation of mg=f, and the movement will maintain this speed in the future. From this point of view, there is a certain relationship between falling speed and mass.

In high school, many physics problems are based on the most ideal situation, while in college, you will continue to build on your high school knowledge, otherwise the results may be contrary to the real situation.

The falling of the object is only affected by gravity, there is no other force, gravity g=mg, the acceleration of gravity is the same, it is a constant g, but because the mass is larger, according to the formula, g is larger, gravity and gravitational acceleration are two different concepts.

Because the acceleration g is the same, the initial velocity of the object is 0, and the falling velocity v=gt, so the velocity of the falling object is the same.

The speed of descent is only related to the initial velocity, altitude, and air resistance. The speed of descent changes quickly and slowly is related to air resistance.

The descent velocity is only related to the initial velocity, height, and air resistance, which in turn is related to the size and shape of the object, but it should be noted that it has nothing to do with the weight of the object.

The speed of the fall is related to the acceleration, ma=mg, a=g, the falling of the object is the acceleration is equal to g, independent of the mass, the exact acceleration calculation formula: ma=mg-f (resistance).

Why does the velocity of this object decrease when it rises and increases when it falls?

Answer: When the object is moving upward, gravity does negative work, the gravitational potential energy increases, and the kinetic energy decreases, so the velocity decreases;

And when the object descends, the gravitational force does positive work, the gravitational potential energy decreases, and the kinetic energy increases, so the velocity increases. Of course, this is the result of only gravity, when the mechanical collapse energy is conserved.

I believe everyone still remembers that when I was in school, there was a text called "Two Iron Balls Falling at the Same Time", which said that Aristotle believed that heavy objects fall faster than light objects, so when the mass of the iron tree is let go at the same height as the small iron ball, the large iron ball will land first than the small iron ball, but it was later denied by Galileo. Galileo believed that after two such iron balls fell at the same height and with the same initial velocity, the two iron balls would hit the ground at the same time. Is it true that someone who says that a heavy object falls faster than a lighter object?

Experiments have proved that the statement that heavy objects fall faster than light objects is not true.

Galileo once did an experiment in the Leaning Tower of Pisa, using a large iron ball and a small iron ball, letting go at the same time, and finally, both iron balls hit the ground at the same time. This experiment also proves that heavy objects do not fall faster than light ones. People think this way, it's just some subjective judgments.

2. Why do two iron balls land at the same time?

If the air resistance is not taken into account, the gravitational force experienced by both objects is the same. So the acceleration is the same, if the initial velocity is all zero, or it is equal. Then in the process of falling, the speed will also be consistent.

After falling to the same height, the time taken must be the same. However, if you consider air buoyancy, it is not necessarily the same, because the iron ball is small in size and dense, so the buoyancy is negligible. But for some things with low density, it can't be ignored.

For example, with the same quality of cotton and iron balls, the iron balls must fall fast, because the cotton is large in size, and the air buoyancy is large, that is, the resistance is large. As a result, it will be slower in the process of falling. This is why people often feel that heavy objects fall faster than light ones.

If you don't take into account the air resistance, the speed of a heavy object and a light object is the same, and if you consider the air resistance, because the air resistance of a heavy object is greater than that of a light object, the speed will be faster than that of a light object.

This is acceleration.

Although we know that the acceleration due to gravity is the same for any object. However, the gravitational force of different masses of objects is different.

The gravitational force on the heavy object is also relatively large, and the landing time mainly depends on the acceleration, that is, the resultant force (gravity minus drag) mass. Therefore, the more massive the object, the faster it falls.

Heavy objects and light objects fall just as fast, probably due to different areas underneath, so there may be differences in the speed of falling.

The resistance is different, and if it is in a vacuum, both objects will hit the ground at the same time