h = 600 x 10³ m
V = 7616 x 10³ km/s
R = 6371 x 10³ m
Substituting the values.
T = \(\frac {2 \pi (R + h)}{V}\)
= \(\frac { 2\times \frac { 22 }{ 7 } \left( 6371+600 \right) { 10 }^{ 3 } }{ 7616 } \)
= 5.748 x 10³
= 5748 seconds.
This is T ≈ 96 min

Radius of the earth = R = 6400 km
= 6.4 x 10⁶ m
Height of satellite above the surface of the earth
h = 2000 km
= 2.0 x 10⁶ m
Radius of orbit of the satellite r = R + h
R + h = 6.4 x 10⁶+ 2.0 x 10⁶ m
= 8.4 x 10⁶ m
Velocity = 7600 m/s
To find T = ?
V = \(\frac {2 \pi r}{T}\)
T = \(\frac {2 \pi (R + h)}{V}\)
T = \(\frac {2 \times 3.14 \times 8.4 \times {10}^{6}}{7600}\)
= 6.94 x 10³
T = \(\frac {6.94 \times {10}^{3}}{3600}\) = 0.00192 x 10³
T = 1.92 hrs

Radius of the earth = R = 6400 km
= 6.4 x 10⁶ m
Radius of the orbit of the Moon = r = 3.84 x 10⁵ km or 3.84 x 10⁸ m
g = 9.8 m/s²
To find period of revolution of the Moon.
T = 2π \(\sqrt {\frac {{r}^{3}}{GM}}\)
T = 2π \(\sqrt {\frac {{r}^{3}}{{R}^{2}g}}\)
T = 2 x 3.14 \(\sqrt { \frac { { \left( 3.84\times { 10 }^{ 8 } \right) }^{ 3 } }{ { \left( 6.4\times { 10 }^{ 6 } \right) }^{ 2 }\times 9.8 } } \)
T = 2 x 3.14 \(\sqrt { \frac { { 3.84 }^{ 3 }\times { 10 }^{ 24 } }{ { 6.4 }^{ 2 }\times { 10 }^{ 12 }\times 9.8 } } \)
T = 2.538 x 10⁶s
T = \(\frac {2.358 \times {10}^{6}}{24 \times 60 \times 60}\)
T = 27.3 days
Period of revolution of the earth to revolve around the moon is = 27.3 days.

After the Big Bang, clouds of gases began to compress under gravity to form the building blocks of galaxies. A galaxy is a massive collection of gas, dust and millions of stars and their solar systems.

Millions of pieces of rocks that were left over, when the planets were formed and now revolve around the sun are called as asteroids. The biggest asteroid is Ceres - 946 km across.

1. The main purpose is to provide an international lab for conducting experiments in space, as the space environment is nearly impossible to reproduce here on earth .
2. The micro gravity environment present in the ISS provides ideal conditions for doing many scientific researches especially in biology, human biology, physics, astronomy and meteorology.

1. Meteors are small pieces of rocks scattered throughout the solar system .
2. They travel with high speed, they come close to the earth's atmosphere and are attracted by the gravitational force of the earth .
3. Most of them are burnt up by the heat generated due to friction in the earth's atmosphere. They are called Meteors .
4. Some of the bigger meteors may not be burnt completely and they fall on the surface of the earth, these are called meteorites.

1. The four large planets Jupiter, Saturn, Uranus and Neptune spread out in the outer solar system, that slowly orbit the Sun are called outer planets.
2. They are known as gas giants and are called gaseous planets, because they have hydrogen, helium and other gases in huge amounts and have very dense atmosphere
3. These planets have rings around them. These rings are actually tiny pieces of rock covered with ice.

1. Dark matter gets its name because it cannot be seen with any type of instrument that we have today around 27% of universe is made up of dark matter.
2. Dark energy is something that fills all space around 68% of the universe is dark energy.
3. The theory of dark energy helps us to explain why the universe is expanding.

According to Big - Bang theory all the matter in the universe was concentrated in a single point of hot dense matter. About 13.7 billion years ago, an explosion occurred and ejected all the matter in all directions in the form of galaxies.