"Space Navigation" Gravity and Space Navigation PPT Courseware

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"Space Navigation" Gravity and Space Navigation PPT Courseware

Part 1: Essential knowledge and foundation of literacy

1. The first cosmic speed

[Thinking] As shown in the figure, an object is thrown horizontally. If the speed is large enough, the object will no longer fall to the ground. It will move around the earth and become an artificial satellite of the earth. What force makes the object move around the earth?

Tip: The gravitational force between the Earth and objects.

(1) Derivation of the speed of an object around the earth: The motion of an object around the earth can be regarded as a uniform circular motion. Universal gravity provides the centripetal force required for the movement of the object, which is _____=m. From this, we can solve: v=_____(m is the mass of the earth) , r is the radius of the object making circular motion).

(2) Numerical value: Given the mass of the earth, approximately replace r with the radius R of the earth, and calculate v = _____ = _________. This is the speed at which an object moves in a uniform circular motion near the earth, which is called the first cosmic velocity.

2. The second cosmic speed

When the speed of the aircraft is equal to or greater than __________, it will overcome the earth's gravity and leave the earth forever. We call __________ the second cosmic speed.

3. The third cosmic speed

If an aircraft is launched near the ground and is to break away from the gravitational pull of the sun and fly outside the solar system, its speed must be equal to or greater than __________. This speed is called the third cosmic speed.

Space Navigation PPT, Part 2: Key Competencies·Quality Formation

1. Qualitative analysis and quantitative calculation of the first cosmic velocity

Task 1 Qualitative analysis of the velocity of the first universe

1. First cosmic speed: The first cosmic speed is the speed that an artificial satellite must have to orbit the earth in a uniform circular motion, that is, the orbiting speed of a near-Earth satellite.

2. Determining factors: From the calculation formula v= of the first cosmic velocity, it can be seen that the value of the first cosmic velocity is determined by the central celestial body. The size of the first cosmic velocity depends on the mass M and radius R of the central celestial body, and has nothing to do with the satellite. .

3. "Minimum launch speed": If the launch speed is lower than the first cosmic speed, the launched satellite will return to the earth due to the gravity of the earth. Therefore, the first cosmic speed is the minimum speed for launching artificial satellites.

4. "Maximum orbiting speed": Among all satellites orbiting the earth in uniform circular motion, the orbital radius of the near-Earth satellite is the smallest. From _________, it can be obtained that the smaller the orbital radius, the greater the linear speed, so in these Among satellites, the linear velocity of the near-Earth satellite, that is, the first cosmic velocity, is the maximum orbiting velocity.

【Think·Discussion】

Can an earth satellite flying at an altitude of 100 to 200 km be said to be flying near the ground? Why? (Scientific thinking)

Tip: Yes. Because 100-200 km can be ignored compared with the earth's radius of 6,400 km.

[Typical example demonstration 1] (Multiple choice) Regarding the first cosmic velocity, the following statement is correct ()

A. It is the minimum speed of artificial earth satellites flying around the earth

B. It is the speed of artificial satellites in low-Earth circular orbit

C. It is the minimum launch speed for satellites to enter low-Earth circular orbit

D. It is the maximum speed of the artificial satellite when it is launched

Task 2 Quantitative calculation method of the velocity of the first universe

1. According to the gravitational acceleration of the planet's surface, its first cosmic velocity can be calculated based on mg=m.

2. According to the movement of the planet’s near-Earth satellites, its first cosmic velocity can be calculated based on the following

【Literacy Training】

1. (Multiple choice) The first cosmic velocity is the speed of an object in uniform circular motion around the earth near the surface of the earth, then there is ()

A. The greater the mass of the launched object, the greater the first cosmic velocity.

B. The smaller the mass of the launched object, the greater the first cosmic velocity

C. The first cosmic velocity has nothing to do with the mass of the launched object

D. The first cosmic velocity is related to the mass of the earth

2. If the first cosmic velocity of the earth is 8 km/s, the mass of a planet is 6 times that of the earth, and the radius is 1.5 times that of the earth, the first cosmic velocity of this planet is about ()

A.16 km/s B.32 km/s

C.4 km/s D.2 km/s

2. Artificial Earth Satellite

Task 1 Orbital characteristics of artificial earth satellites

1. The laws followed by satellite motion: When a satellite moves in an elliptical orbit around the earth, the center of the earth is at a focus of the ellipse, and the relationship between the satellite's period and its semi-major axis follows Kepler's third law.

2. The center of the satellite orbit: When the satellite moves in a circular orbit around the earth, the earth's gravitational force on the satellite provides the centripetal force for the satellite to move around the earth, and the gravitational force points to the center of the earth, so the center of the earth must be the center of the satellite's circular orbit.

3. Satellite’s orbit: The satellite’s orbital plane can be within the equatorial plane (such as synchronous satellites), pass over the poles (polar orbit satellites), or can be at any angle to the equatorial plane, as shown in the figure.

[Typical Example 1] As shown in the figure, the correct statement about the orbit of the artificial earth satellite is ()

A.a, b, and c may all be satellite orbits

B. The satellite orbit can only be a

C.a and b may both be satellite orbits

D.b may be the orbit of a synchronous satellite

[Analysis] Choose C. Earth satellites move in a uniform circle around the earth, and the center of the circle is the center of the earth. Therefore, the orbital plane of all earth satellites must pass through the center of the earth. Therefore, a and b may be satellite orbits, but c cannot be satellite orbits. Therefore, A and B are wrong. , C is correct; the orbit of the synchronous satellite must be in the equatorial plane, so b cannot be the orbit of the synchronous satellite, so D is wrong.

Mission 2 Geostationary Satellite

1. Geosynchronous satellite: It is located above the earth's equator and is stationary relative to the ground. Its angular velocity is the same as the earth's rotation angular velocity. It is widely used in communications and is also called synchronous communication satellite.

2. Characteristics of geosynchronous satellites:

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Update Time: 2024-10-05

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