What is Gravitation?
Gravitation is the force that pulls objects towards each other because of their masses. For example, the Earth pulls you towards it, which is why you don’t float in the air!
Universal Law of Gravitation
Newton explained that any two objects in the universe attract each other. The force between them depends on:
- Their masses (m1m_1m1 and m2m_2m2).
- The distance (rrr) between them.
The formula is:F=Gm1m2r2F = G \frac{m_1 m_2}{r^2}F=Gr2m1m2
Where:
- GGG is a constant value: 6.67×10−11 Nm2/kg26.67 \times 10^{-11} \, \text{Nm}^2/\text{kg}^26.67×10−11Nm2/kg2
Gravity on Earth
The Earth pulls everything towards its center. This pull creates acceleration due to gravity, denoted by ggg, which is about 9.8 m/s² near the surface.
The formula to calculate ggg is:g=GMR2g = \frac{GM}{R^2}g=R2GM
Where:
- MMM: Mass of Earth.
- RRR: Radius of Earth.
Gravitation – Class 11 CBSE
What is Gravitation?
Gravitation is the force that pulls objects towards each other because of their masses. For example, the Earth pulls you towards it, which is why you don’t float in the air!
Universal Law of Gravitation
Newton explained that any two objects in the universe attract each other. The force between them depends on:
- Their masses (m1m_1m1 and m2m_2m2).
- The distance (rrr) between them.
The formula is:F=Gm1m2r2F = G \frac{m_1 m_2}{r^2}F=Gr2m1m2
Where:
- GGG is a constant value: 6.67×10−11 Nm2/kg26.67 \times 10^{-11} \, \text{Nm}^2/\text{kg}^26.67×10−11Nm2/kg2.
Gravity on Earth
The Earth pulls everything towards its center. This pull creates acceleration due to gravity, denoted by ggg, which is about 9.8 m/s² near the surface.
The formula to calculate ggg is:g=GMR2g = \frac{GM}{R^2}g=R2GM
Where:
- MMM: Mass of Earth.
- RRR: Radius of Earth.
Changes in Gravity
- When you go up (Altitude):
- Gravity becomes weaker as you move farther from Earth.
- When you go down (Depth):
- Gravity decreases as you go below the surface.
- Across Earth (Latitude):
- Gravity is slightly stronger at the poles and weaker at the equator.
Kepler’s Laws of Planetary Motion
- Planets orbit in ellipses, not perfect circles.
- The closer a planet is to the Sun, the faster it moves.
- A planet’s orbital time depends on its distance from the Sun: farther planets take longer.
Escape Velocity
If you throw something fast enough, it can leave Earth’s pull entirely! This speed is called escape velocity, which is about 11.2 km/s.
Satellites
- Orbital Velocity: The speed needed to keep a satellite in orbit (around 8 km/s near Earth).
- Geostationary Satellites: Satellites that always stay above the same spot on Earth. These are used for TV and communication.
Weightlessness
Astronauts in space feel weightless because they’re falling freely around the Earth, just like their spaceship. This is why objects float in space!
Why Is This Important?
Gravitation explains why:
- Planets orbit stars.
- Tides happen.
- Satellites stay in space.
Understanding it helps us explore space and predict the motion of heavenly bodies!
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