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Gravitation
1. Gravitation
Gravitation is the force of attraction between any two objects having mass. This force: keeps planets in their orbits causes objects to fall towards the Earth is present between all bodies in the universe
2. Universal Law of Gravitation
Every object in the universe attracts every other object with a force that: is directly proportional to the product of their masses is inversely proportional to the square of the distance between their centres
Mathematical Form:
F= G 𝒎𝟏 𝒎𝟐 𝒓𝟐 Where: F = gravitational force G = universal gravitational constant m₁, m₂ = masses of the two objects r = distance between their centers
3. Importance of Gravitation
Gravitation: binds objects to the Earth keeps the Moon around the Earth keeps planets around the Sun
causes tides in oceans
4. Free Fall
When an object falls towards the Earth only under the influence of gravity, it is called free fall. During free fall: acceleration is constant air resistance is neglected
5. Acceleration due to Gravity (g)
The acceleration produced in a freely falling body due to Earth’s gravity is called acceleration due to gravity. Symbol: g Value near Earth’s surface: 9.8 m/s²
6. Relation Between g and G
𝑮𝑴 𝑹𝟐 Where: G = universal gravitational constant M = mass of the Earth R = radius of the Earth
7. Mass
Mass is the quantity of matter contained in an object. Properties:
Pressure is the force acting per unit area. Formula: 𝑭𝒐𝒓𝒄𝒆 𝑨𝒓𝒆𝒂 Unit: Pascal (Pa)
11. Buoyancy
The upward force exerted by a fluid on an object immersed in it is called buoyant force or upthrust. It depends on: density of the fluid volume of the object immersed
12. Archimedes’ Principle
When a body is immersed fully or partially in a fluid, it experiences an upward force equal to the weight of the fluid displaced by it.
13. Density
Density is the mass per unit volume of a substance. Formula: 𝑴𝒂𝒔𝒔 𝑽𝒐𝒍𝒖𝒎𝒆 Unit: kg/m³
14. Relative Density
Relative density is the ratio of density of a substance to the density of water. It has no unit.
15. Important Points
Gravitation acts between all objects having mass Weight depends on g, mass does not Pressure increases when area decreases Objects float if buoyant force is equal to or greater than weight Relative density has no unit
