"The Law of Universal Gravity" Gravity and Space Navigation PPT High-Quality Courseware

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"The Law of Universal Gravity" Gravity and Space Navigation PPT High-Quality Courseware

Part One: Core Competency Goals

physical concepts

Understand the existence of gravity between the sun and planets, and master the content and expression of the law of universal gravitation.

scientific thinking

According to Kepler's law of planetary motion and Newton's third law, the gravitational formula between the sun and the planets is derived. Through the moon-earth test, the gravitational force between the sun and the planets is generalized into the law of universal gravitation, and the applicable conditions and applications of the expression of universal gravitation are mastered.

Scientific attitude and responsibility

A rigorous scientific attitude, a scientific spirit and method of seeking truth and simplicity, and a passion for exploring the truth of the universe.

Law of Universal Gravity PPT, Part 2 Content: Pre-class Study

Knowledge point 1: The gravitational force between the planet and the sun

[Viewing pictures to help students]

(1) Why do apples fall from the tree to the ground instead of flying into the sky?

(2) Objects around us are all affected by the gravity of the earth, so does the earth also be affected by the gravity of the sun? Why does the earth not fall on the surface of the sun, but revolve around the sun?

1. Derivation process

As shown in the figure on the right, assuming that the mass of the planet is m, the speed is v, and the distance between the planet and the sun is r, then the centripetal force of the planet moving in a uniform circular motion around the sun is F=__________①

Astronomical observations can measure the period T of the planet's revolution, and based on this, the speed of the planet can be calculated v = _________ ② Combined ① ② After sorting, we get F = ___________ ③

2. Expression: F=Gm too mr2

The quantity G in the formula has nothing to do with the sun or planets. The direction of gravity between the sun and the planets is along the line connecting them.

The apple falling to the ground is caused by the earth's gravitational pull on the apple.

It is precisely because of the gravitational pull of the sun that the planets can revolve around the sun.

Knowledge Points February—Ground Inspection

[Viewing pictures to help students]

Is the Earth's gravity on the satellite the same as the Moon's gravity on the Chang'e-2? Are the rules followed the same?

[Thinking and Judging]

(1) The moon moves in a uniform circular motion around the earth because the forces on the moon are balanced. ( )

(2) The centripetal force of the moon's circular motion is generated by the earth's gravitational pull on it. ( )

(3) The gravitational pull of the earth on the moon and the gravitational pull of the earth on objects on the ground are two forces with different properties. ( )

Knowledge point 4: Gravitational constant

1. Determination of gravitational constant

British physicist Cavendish used a torsion balance device in the laboratory to obtain the G value more accurately. At that time, he measured G=6.745×10-11 N·m2/kg2. The recommended value G=6.674 08(31)×10-11 N·m2/kg2 in 2014 by the International Committee on Scientific and Technological Data is usually taken as G=6.67×10-11 N·m2/kg2.

2. The significance of measuring the gravitational constant

(1) Cavendish used a torsion balance device to confirm the existence of universal gravitation and the correctness of the law of universal gravitation by changing the mass and distance of the ball.

(2) The universality of the gravitational constant has become strong evidence for the correctness of the law of universal gravitation.

Law of Universal Gravitation PPT, Part 3: Core Research

Core Points: Understanding the Law of Gravity

[Problem exploration]

There is a gravitational force between the sun and the planets, between the earth and the moon, and between any objects.

(1) What is the meaning of r in the formula F=Gm1m2r2?

(2) Can the gravitational force between any two objects be calculated using the formula F=Gm1m2r2?

[Explore and summarize]

1. Explanation of the expression of the law of universal gravitation F=Gm1m2r2

(1) Gravitational constant G: G=6.67×10-11 N·m2/kg2; its physical meaning is: the gravitational constant is numerically equal to the mutual attraction of two particles with a mass of 1 kg when they are 1 m apart.

(2) Distance r: r in the formula is the distance between two particle points. For a sphere with uniform mass distribution, it is the distance between the centers of the two spheres.

2. Applicable conditions for F＝Gm1m2r2

(1) The formula of the law of universal gravitation is suitable for calculating the interaction between particles. When the distance between two objects is much larger than the scale of the object itself, this formula can be used to approximately calculate the universal gravitation between the two objects.

(2) The interaction between spheres with uniform mass distribution can be calculated by this formula, where r is the distance between the centers of the two spheres.

(3) The gravitational force between a uniform sphere and a particle outside the sphere can also be calculated using this formula, where r is the distance from the center of the sphere to the particle.

3. Four characteristics of gravity

[For training 1] (Multiple choice) The correct understanding of universal gravitation and the law of universal gravitation is ()

A. There is no gravitational force between two objects that cannot be regarded as particles.

B. Only the gravitational force between two objects that can be regarded as particle points can be calculated with F=

C. It is known from F= that when the distance r between two objects decreases, the gravitational force between them increases

D. The measurement of the gravitational constant G proves the correctness of the law of universal gravitation.

Core Point 2: Simple Application of the Law of Gravity

1. There is a gravitational force between any two objects, but F=Gm1m2r2 has its applicable range. When calculating the magnitude of the gravitational force, pay attention to determine whether it meets the applicable conditions.

2. When applying the expression of the law of universal gravitation F = Gm1m2r2 for relevant calculations, r refers to the distance between two particles (or two sphere centers, or particle points and sphere centers), not the distance between two objects (spheres).

[Examination Cases]

Example 2 . It is known that the mass of the sun is about 2.7×107 times the mass of the moon, and the radius of the earth's orbit around the sun is about 400 times the radius of the moon's orbit around the earth. Regarding the gravitational pull of the sun and the moon on the same mass of sea water on the earth, which of the following statements is correct ()

A. The sun’s gravity is much greater than the moon’s gravity

B. The gravity of the sun is not much different from the gravity of the moon

C. The moon’s gravitational pull on seawater in different areas is equal

D. The moon’s gravitational pull on seawater in different areas is different.

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"The Law of Universal Gravity" Universal Gravity and Space Navigation PPT:

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Update Time: 2024-09-05

This template belongs to Physics courseware People's Education Press High School Physics Compulsory Course II industry PPT template

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