Notes : Earth Satellite it's type and Principle of Launching Satellite - Param Himalaya

Notes : Earth Satellite it's type and Principle of Launching Satellite - Param Himalaya 

What is a Earth Satellite?

A satellite is a small body that revolves around a planet in a definite orbit due to gravitational attraction.

Types of Satellites

1. Natural Satellite

A satellite that revolves around a planet naturally is called a natural satellite.

Example: The Moon is the natural satellite of the Earth.

2. Artificial Satellite

A man-made object launched into space to revolve around the Earth or another planet is called an artificial satellite.

Difference Between Natural and Artificial Satellites

Natural Satellite	Artificial Satellite
Formed naturally.	Made and launched by humans.
Revolves around a planet due to natural processes.	Placed into orbit for specific purposes.
Example: Moon.	Example: Aryabhata, INSAT, Rohini.
No human control.	Can be monitored and controlled from Earth.

Uses of Artificial Satellites

• Communication
• Weather forecasting
• Remote sensing
• Navigation
• Scientific research
• Military applications

Important Artificial Satellites

• Sputnik-I (USSR, 1957) – First artificial satellite.
• Aryabhata (India, 19 April 1975) – First Indian satellite.
• Bhaskara-I (7 June 1979)
• Rohini-1
• APPLE (19 June 1981)
• INSAT Series
• IRS Series

A large number of satellites have been launched by ISRO (Indian Space Research Organisation).

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8.9.1 Principle of Launching a Satellite

Principle

Consider a body thrown horizontally from the top of a very high tower.

Case 1: Low Velocity

When the body is thrown with a small horizontal velocity, it follows a parabolic path under the influence of gravity and falls back to the Earth.

Case 2: Higher Velocity

If the horizontal velocity is increased, the body travels a greater distance before striking the Earth's surface.

Case 3: Orbital Velocity

When the horizontal velocity becomes equal to the orbital velocity, the curvature of its path becomes equal to the curvature of the Earth.

As a result, the body continuously falls towards the Earth but never reaches it. It keeps revolving around the Earth in a circular orbit and becomes an artificial satellite.

Important Note

The motion of a satellite around the Earth is an example of a freely falling body.

The gravitational force continuously provides the necessary centripetal force required for orbital motion.

Diagram Explanation

• Path A → Low velocity; body falls near the Earth.
• Path B → Higher velocity; body falls farther away.
• Path C → Orbital velocity attained; body revolves around the Earth as a satellite.

Thus, a satellite remains in orbit because it is continuously falling towards the Earth while moving forward with sufficient horizontal velocity.

Key Points

• A satellite revolves around a planet in an orbit.
• Satellites are of two types: natural and artificial.
• The Moon is Earth's natural satellite.
• Sputnik-I was the first artificial satellite.
• Aryabhata was India's first satellite.
• A satellite is launched by giving it sufficient horizontal velocity.
• At orbital velocity, the satellite continuously falls around the Earth without hitting it.
• The gravitational force acts as the centripetal force for orbital motion.

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Frequently Asked Questions (FAQ)

Q1. What is a satellite?

A satellite is a body that revolves around a planet in a fixed orbit.

Q2. What is a natural satellite?

A naturally occurring body revolving around a planet is called a natural satellite.

Q3. What is an artificial satellite?

A man-made object launched into space to revolve around a planet is called an artificial satellite.

Q4. What was the first artificial satellite?

Sputnik-I, launched by the USSR in 1957, was the first artificial satellite.

Q5. Which was India's first artificial satellite?

Aryabhata, launched on 19 April 1975, was India's first artificial satellite.

Q6. Why does a satellite not fall on the Earth?

Because it has sufficient horizontal velocity and continuously falls around the Earth rather than directly towards it.

Q7. What force keeps a satellite in orbit?

The gravitational force of the Earth provides the necessary centripetal force.

Q8. Is a satellite a freely falling body?

Yes, a satellite is continuously falling towards the Earth under gravity while moving forward with high speed.

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MCQs

1. A satellite is:

   A) A star
   B) A body revolving around a planet
   C) A planet
   D) A comet

   Answer: B

2. Which of the following is a natural satellite?

   A) Aryabhata
   B) INSAT
   C) Moon
   D) Sputnik-I

   Answer: C

3. The first artificial satellite was:

   A) Aryabhata
   B) Rohini
   C) Sputnik-I
   D) APPLE

   Answer: C

4. India's first artificial satellite was:

   A) Rohini
   B) INSAT
   C) Aryabhata
   D) APPLE

   Answer: C

5. A satellite remains in orbit because:

   A) There is no gravity in space
   B) It continuously falls towards Earth with sufficient horizontal velocity
   C) Air supports it
   D) It has no mass

   Answer: B

6. The force acting as centripetal force for a satellite is:

   A) Magnetic force
   B) Electric force
   C) Gravitational force
   D) Frictional force

   Answer: C

7. When a body is given orbital velocity, it:

   A) Falls immediately
   B) Escapes Earth
   C) Revolves around Earth as a satellite
   D) Stops moving

   Answer: C

8. Artificial satellites are mainly used for:

   A) Communication
   B) Weather forecasting
   C) Remote sensing
   D) All of these

   Answer: D