Definitions [2]
Define time period of a satellite.
Time taken by the satellite to complete one revolution round the Earth is called time period.
Time period, T = `"Distance covered"/"Orbital velocity"`
T = `"2πr"/"v"`
Definition: Artificial Satellite
If a manmade object revolves around the earth or any other planet in a fixed orbit it is called an artificial satellite.
Formulae [1]
Formula: Escape Velocity
vesc = \[\sqrt{\frac{2\mathrm{~GM}}{\mathrm{R}}}\]
where
- G = Gravitational constant
- M = mass of the planet
- R = Radius of the planet
Theorems and Laws [1]
Write the Kepler’s laws.
- Kepler’s first law: The orbit of a planet is an ellipse with the sun at one of the foci.
- Kepler’s second law: The line joining the planet and the sun sweeps equal areas in equal intervals of time.
- Kepler’s third law: The square of the orbital period of revolution of a planet around the Sun is directly proportional to the cube of the mean distance of the planet from the Sun.
Key Points
Key Points: The Universe
- The universe is an ever-expanding expanse encompassing all matter, energy, time, and celestial bodies.
- It is primarily structured by billions of galaxies, which are massive, gravitationally bound collections of stars and planetary systems.
- Our solar system is located within the Milky Way, which forms part of the Local Group of galaxies alongside its closest major neighbour, the Andromeda galaxy.
- Scientific consensus suggests the universe originated from a massive explosion known as the Big Bang approximately 13.7 to 15 billion years ago.
- Earth was formed around 4.5 billion years ago from a collapsing gaseous cloud, with the first life emerging roughly 500 million years later.
Key Points: Artificial Satellites
- Natural satellites are natural (like the Moon); artificial satellites are manmade and orbit planets.
- Sputnik was the first artificial satellite, launched by the USSR in 1957.
- Satellites use solar panels for energy and send/receive signals.
- Types of satellites: weather, communication, broadcast, navigation, military, and Earth observation.
- India uses INSAT, GSAT, IRNSS, and IRS satellites, launched by GSLV and PSLV rockets.
Key Points: Orbits of Artificial Satellites
- Satellites are placed into orbit using launchers and require a specific tangential speed (the critical velocity).
- Low Earth Orbits (180–2000 km) are used for space stations and weather studies.
- Medium Earth Orbits (2000–35780 km) are used for GPS and polar satellites.
- High Earth Orbits (≥35780 km) include geostationary satellites used for TV, phone, and weather.
- The higher the orbit, the lower the speed needed; satellite speed doesn’t depend on its mass.
