"Achievements in the Theory of Gravity" Gravity and Space Navigation PPT

"Achievements in the Theory of Gravity" Gravity and Space Navigation PPT

Part One: Learning Objectives

1. Understand the important application of the law of universal gravitation in astronomy;

2. Be able to use the law of universal gravitation to calculate the mass of celestial bodies;

3. Understand and apply the law of universal gravitation to the ideas and methods of dealing with celestial problems.

Achievements in the Theory of Gravity PPT, Part 2: Review Review

1. What is the formula of centripetal force for an object to move in a circular motion? Write the relationship between centripetal force, linear velocity, angular velocity and period respectively.

2. What is the content of the law of universal gravitation? How to express it with formula?

3. What is the relationship between gravity and universal gravitation?

When an object m is at a position with latitude θ, the gravitational force points to the center of the earth and is decomposed into two components: the centripetal force and the gravity that cause m to move around the earth's axis with the rotation of the earth.

Gravity is a component of universal gravitation. When the rotation of the earth is ignored, gravity can be considered to be numerically equal to the magnitude of universal gravitation.

Achievements in the Theory of Gravity PPT, Part 3: Introduction of New Lesson

"Give me a fulcrum and I can move the ball."

So how do we know the mass of the huge Earth?

1. Idea: The mass of the earth cannot be measured with a scale.

Can the law of universal gravitation help us?

Gravity is a component of universal gravitation. When the rotation of the earth is ignored, gravity can be considered to be numerically equal to the magnitude of universal gravitation.

Weigh the mass of the earth

The famous writer Mark Twain said passionately:

"Science is really fascinating. Based on scattered facts and a little guesswork, you can gain so much!"

Thinking: The mass of the earth can be calculated by applying universal gravitation. Can the mass of the sun be calculated?

1. What is the actual shape of the Earth’s orbit? For the convenience of solving the problem, we can usually think of what orbit the earth is orbiting and what movement it is doing?

2. What force provides the centripetal force for the earth’s circular motion?

Calculation of the mass of celestial bodies

Solution idea: The centripetal force of the circular celestial body is exclusively provided by the central celestial body’s gravitational pull.

Note: The mass of the celestial body to be determined (M) has nothing to do with the mass of the ringing celestial body (m)

gold replacement

The gravitational force experienced by an object with mass m on the surface of the earth (star) is equal to its gravity, that is, G = mg. It can be obtained: GM=gR2

Because the two parameters G and M (Earth mass) are often difficult to remember, g and R are easy to remember. Therefore, when making rough calculations, the above substitution is generally used, which avoids the value of the universal gravitational constant G and the value of the mass of the earth M.

Unknown celestial body discovered---Neptune

The orbit of Uranus, the seventh planet discovered in 1781, always deviated to a certain extent from that calculated based on the law of universal gravitation. At that time, some people predicted that there must be an undiscovered new star outside its orbit, which was later discovered. The eighth planet—Neptune.

The actual orbit of Neptune was calculated independently by Adams, a student at the University of Cambridge in the United Kingdom, and Le Verrier, a young French astronomy enthusiast, based on the observation data of Uranus and using the law of universal gravitation.

Pluto was predicted and discovered:

After Neptune was discovered, it was discovered that its orbit was also inconsistent with theoretical calculations. So several scholars used the methods of Adams and Le Verrier to predict the existence of another new planet.

After the prediction was made, in 1930, Tombaugh discovered Pluto, which was later known as the ninth planet in the solar system.

Achievements in the Theory of Gravity PPT, Part 4: Frequently Asked Question Types

Question Group 1: Calculate the mass and density of celestial bodies

Question 1 [2019•Guangdong Foshan No. 1 Middle School Grade 1 Test] (1) Kepler’s third law states: The cube of the semi-major axis a of a planet’s elliptical orbit around the sun is proportional to the square of its revolution period T. That is =k, k is a constant that is the same for all planets. Treat the motion of the planets around the sun as circular motion, please deduce the expression of the constant k in the solar system (it is known that the gravitational constant is G and the mass of the sun is M);

(2) Kepler's law is not only applicable to the solar system, it is also true for all gravitational systems with central celestial bodies (such as the earth-moon system). It has been determined that the distance between the moon and the earth is 3.84×108m, the period of the moon’s motion around the earth is 2.36×106 s, and the radius of the earth is 6 400 km. Try to estimate the mass M and density ρ of the earth. (G=6.67×10-11 N·m2/kg2, all calculation results retain one significant figure)

Achievements in the Theory of Gravity PPT, Part 5: Content Summary

1. The application of the law of universal gravitation in astronomy generally has two ideas:

(1) The gravity of objects on the ground (or the surface of a certain planet) is approximately equal to the universal gravitation.

(2) The centripetal force required to orbit a celestial body is provided by the gravitational pull of the central celestial body on the surrounding celestial body.

2. Understand the importance of the law of universal gravitation in astronomy.

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"The Achievements of the Theory of Gravity" Gravity and Space Navigation PPT high-quality courseware:

"The Achievements of the Theory of Gravity" Gravity and Space Navigation PPT High-quality Courseware Part One: Core Competency Objectives Physical Concepts Understand the important application of the law of gravity in astronomy. Scientific thinking: Master the method of calculating the mass and density of celestial bodies. ..

"The Achievements of the Theory of Gravity" Excellent Courseware of Gravity and Space Navigation PPT:

"The Achievements of the Theory of Universal Gravity" Excellent Courseware on Gravity and Space Navigation PPT Part One Contents: Learning Objectives 1. Understand the important application of the law of universal gravitation in astronomy. 2. Understand the basic ideas of weighing the earth's mass and calculating the sun's mass, and be able to use everything lead..

"Achievements in the Theory of Gravity" Gravity and Space Navigation PPT Courseware:

"The Achievements of the Theory of Universal Gravity" Gravity and Space Navigation PPT Courseware Part One Content: Foundation of Essential Knowledge Literacy 1. Weighing the Mass of the Earth [Thinking] If the earth cannot be weighed with a balance, can it be weighed by the law of universal gravitation? Tip: Yes 1...