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

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

Part One: Learning Objectives

(1) Understand the existence of gravity between the sun and the planets;

(2) Be able to derive the expression of gravity between the sun and the planets based on Kepler’s law of planetary motion and Newton’s third law;

(3) Understand the ideas and process of deriving the law of universal gravitation, understand the meaning of the law of universal gravitation, and master the formula of the law of universal gravitation;

(4) Know that there is universal gravitation between any objects and follow the same laws.

Law of Universal Gravitation PPT, Part 2: Knowledge Review: Kepler’s Three Laws

Kepler's first law - the law of orbits

All planets move around the sun in elliptical orbits of different sizes.

The Sun is at one focus of these ellipses;

Kepler's second law - area law

For each planet, the line connecting the Sun and the planet sweeps out equal areas in equal times;

Kepler's third law - periodic law

The ratio of the cube of the semi-major axis of the orbits of all planets to the square of the revolution period is equal.

Law of Universal Gravitation PPT, Part 3: Scientific Footprints

All objects have a tendency to merge.

The motion of the planets is affected by magnetic forces from the sun, which are inversely proportional to distance.

There is rotating material (ether) around the planet that acts on the planet, causing the planet to move around the sun.

The motion of the planets is due to the attraction of the Sun, and the magnitude of the force is inversely proportional to the square of the distance from the Sun.

Law of Universal Gravitation PPT, Part 4: Building the Model:

Temptation: The actual motion of the planet is elliptical motion, but we don’t understand the laws of elliptical motion yet, so what should we do? What kind of movement can it be reduced to?

Temptation: Since the motion of the planet around the sun is simplified to circular motion. So can the motion of planets around the sun be regarded as uniform circular motion or variable speed circular motion?

Temptation: The sun provides centripetal force to the planet's gravity. What is the quantitative relationship between the magnitude of this force?

Law of Universal Gravitation PPT, Part 5: The Gravity of Planets on the Sun:

The gravitational pull of the sun on a planet is directly proportional to the mass of the star receiving the force, and inversely proportional to the square of the distance between the planet and the sun.

The gravitational force F′ of a planet on the sun is directly proportional to the mass of the sun and inversely proportional to the square of the distance between the planet and the sun.

Determination of gravitational constant:

Device introduction: T-shaped frame, quartz wire, mirror ruler, M ball and m ball ⑵Measurement principle introduction: When the torsion scale reaches equilibrium, the gravitational moment is equal to the resistance moment of the quartz wire. The quartz wire rotation angle can be measured by the mirror ruler, and the quartz wire It can be seen from the rotation angle that the torsional moment is equal to the gravitational moment, so the universal gravitation can be measured, and then the gravitational constant G can be measured.

Conditions for the formula to apply:

1. Universal gravitation exists between all objects, but the formula of universal gravitation is applicable to the calculation of the gravity between particle points. r is the distance between particle points. The shape and size of the two objects have negligible influence on their distance, r≫R;

2. The gravitational force between two spheres with uniform mass distribution can also be calculated by the above formula, and r is the distance between the centers of the two spheres;

3. The gravitational force between a sphere with uniform mass distribution and a particle outside the sphere, r is the distance from the center of the sphere to the particle.

Law of Universal Gravity PPT, Part 6 Content: Nature of Universal Gravity:

1. Universality

Universal gravity exists between any two objects with mass. It is one of the basic interactions between matter in nature.

2. Macroscopic nature

Although there is universal gravitation between general objects, it is very small. Only the gravitation between celestial bodies or between celestial bodies is more significant. Therefore, when it comes to the movement of celestial bodies. Only then do we consider the force of gravity

3. Mutuality

The effect of universal gravitation is mutual and conforms to Newton's third law

4. Independence

The gravitational force between two objects is only related to their own mass and the distance between them, and has nothing to do with whether there is other matter around them

The law of universal gravitation PPT, Part 7: Frequently tested questions

Question group January----ground inspection

Question 1 [2019•Guangdong Zhongyuan Middle School Grade 1 Test] In order to unify the forces in the sky and the forces on the earth, Newton conducted the famous "Moon-Earth Test". The "month-to-ground test" compares ()

A. The gravitational acceleration of objects on the moon’s surface and the centripetal acceleration of the earth’s revolution

B. The gravitational acceleration of objects on the moon’s surface and the gravitational acceleration of objects on the earth’s surface

C. Centripetal acceleration of the moon’s revolution and centripetal acceleration of the earth’s revolution

D. Centripetal acceleration of the moon’s revolution and gravitational acceleration of objects on the earth’s surface

[Analysis] The "Moon-Earth Test" compares the centripetal acceleration of the moon's revolution around the earth and the gravitational acceleration of objects on the earth's surface, and concludes that the force in the sky and the force on the ground are unified.

【Answer】D

[Comments] Know the history of physics, the main steps and physical methods used by physicists in corresponding scientific research.

Question 2 [2018·Beijing Volume] If you want to test whether "the force that makes the moon move around the earth" and "the force that makes the apple fall to the ground" follow the same law, when it is known that the distance between the moon and the earth is about 60 times the radius of the earth, needvalidate()

A. The force with which the earth attracts the moon is approximately the same as the force with which the earth attracts apples.

B. The acceleration of the moon’s revolution is approximately the acceleration of an apple falling to the ground.

C. The acceleration of free fall on the moon's surface is about that of the earth's surface

D. The gravitational force an apple experiences on the moon’s surface is approximately that on the earth’s surface.

Question Group 2 Understanding the Law of Universal Gravity

Question 3 [2019•Guangdong Chaoyang Experimental School Senior Grade 1 Test] Regarding the expression of the law of universal gravitation F=____, the correct statement below is ()

A. G in the formula is the gravitational constant. It is not measured experimentally, but is artificially prescribed.

B. When the distance r between the surfaces of two objects approaches zero, the universal gravitation tends to infinity.

C. The gravitational forces on m1 and m2 are always equal to each other, regardless of whether m1 and m2 are equal.

D. The gravitational forces m1 and m2 receive from each other are always equal in magnitude and opposite in direction. They are a pair of balanced forces.

[Analysis] Error A: G in the formula is the gravitational constant. It is not artificially prescribed, but measured experimentally.

B is wrong: The law of universal gravitation only applies to the interaction between particles. When the distance r between the surfaces of two objects approaches zero, the law of universal gravitation no longer holds.

C is right, D is wrong: The gravitational forces m1 and m2 exert on each other are action and reaction forces, not balancing forces. They are always equal in size and opposite in direction, regardless of whether m1 and m2 are equal.

【Answer】C

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

"Law of Universal Gravity" Gravity and Space Navigation PPT High-quality Courseware Part One: Core Competency Objectives 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 planetary movements...

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

"The Law of Universal Gravity" Excellent Gravity and Space Navigation PPT Courseware Part One Content: Learning Objectives 1. Know that the sun's gravity on the planet provides the centripetal force for the planet to move in a circular motion, and be able to use Kepler's third law and Newton's law of motion to deduce that the sun and OK..

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

"The Law of Universal Gravity" Gravity and Space Navigation PPT Courseware Part One Content: Foundation of Essential Knowledge Literacy 1. Gravity between Planets and the Sun [Thinking] On the basis of previous research, Newton believed that any way to change the speed requires a force for planetary motion. ..

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Update Time: 2024-10-17

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