Space Part 3 - Inner and Outer Planet - Gravitational Field Strength
Channel: Physics Partner
Date: 2023-01-10

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Video link to learn more about Newtons law of Gravitation 

https://youtu.be/jO6Xgnz-b0A

Key notes for exam preparation 

Inner planets are the four closest planets to the sun. They are also called the "terrestrial planets" because they are made mostly of rocks and metals. Whereas the four farthest planets from the sun. They are also called the "gas giants" because they are made mostly of gases.

This difference is referred by accretion model for Solar System formation, In planetary science, accretion is the process in which solids agglomerate (piled up) to form larger and larger objects, and eventually planets are produced. 

This model is the most commonly accepted mechanism. In this model a rocky core forms through the concentration of small planetary until it is sufficiently massive to accrete a gaseous envelope.
This accretion is the certain result of gravitational forces operating on all scales, and on all types of material such as gas, dust, plasma, even dark matter. 
The region between the stars contains interstellar clouds composed primarily of dust and gas. Over 100 molecules (neutrals, ions, and radicals), mostly carbon-containing compounds, have been identified in interstellar molecular clouds.) The presence of many elements in interstellar clouds of gas and dust has been confirmed 
The rotation of material in the cloud creates the formation of an accretion disc. accretion discs are flattened astronomical objects made of rapidly rotating gas which slowly spirals onto a central gravitating body. The accretion disk forms when diffuse material is attracted to a massive central body, like a black hole. 
• The gravitational field strength at a point describes how strong or weak a gravitational field is at that point.
at the surface of a planet the gravitational field strength depends on the mass of the planet, if mass is greater the gravitational field is also greater whereas the gravitational field strength is weaker with the increasing distance, it means more distance means less gravitational field  
• The gravitational field strength phenomenon is also explained by the Newton’s law of gravitation 
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• How to calculate the time for light to travel a significant distance such as between objects in the Solar System, let see the how long it takes to reach the light from between sun to earth, distance / time. 8.33 minutes
The Sun weighs about 333,000 times as much as Earth. It is so large that about 1,300,000 planet Earths can fit inside of it. Because of the heavy mass of sun, Sun contains most of the mass of the Solar System and this explains why the planets orbit the Sun. Anyway, the basic reason why the planets revolve around, or orbit, the Sun, is that the gravity of the Sun. the gravity of the sun keeps them in their orbits. This gravity is because of heavy mass of the sun as compared to other planets.  Just as the Moon orbits the Earth because of the pull of Earth's gravity, the Earth orbits the Sun because of the pull of the Sun's gravity.
A planet's orbital speed changes, depending on how far it is from the Sun. The closer a planet is to the Sun, the stronger the Sun's gravitational pull on it, and the faster the planet moves. The farther it is from the Sun, the weaker the Sun's gravitational pull, and the slower it moves in its orbit.
Planetary orbits are an excellent example of the principle of energy conservation, because over time, a mass in an elliptical orbit converts energy from potential to kinetic and the reverse, while maintaining a constant total energy (the sum of potential and kinetic energy).
Like the case of circular motion, the total amount of mechanical energy of a satellite in elliptical motion also remains constant.