Gravitation

Gravitation is the natural force of attraction between any two objects in the universe. Every object, whether big or small, attracts every other object with this force. This is called the gravitational force.

Newton’s Universal Law of Gravitation:
Every object in the universe attracts every other object with a force which is directly proportional to the product of their masses and inversely proportional to the square of the distance between their centers.
Formula: F = G × (m₁ × m₂) / r²
Here,
F = gravitational force between two objects
m₁ and m₂ = masses of the two objects
r = distance between their centers
G = universal gravitational constant (6.67 × 10⁻¹¹ N·m²/kg²)

Gravity:
The Earth attracts all objects towards its center. This force of attraction is called gravity. Due to gravity, objects fall towards the Earth when dropped.

Acceleration due to Gravity (g):
When an object falls freely under the influence of gravity, it has an acceleration called acceleration due to gravity.
Its value on Earth is about 9.8 m/s².

Mass and Weight:

Mass is the amount of matter in a body. It remains constant everywhere.

Weight is the force with which the Earth attracts a body.
Formula: Weight = Mass × Gravity (W = m × g)
Weight changes from place to place because the value of g changes.

Free Fall:
When an object falls only under the influence of gravity and no other force acts on it, the motion is called free fall.

Thrust and Pressure:
Thrust is the total force acting perpendicularly on a surface.
Pressure is the force acting per unit area.
Formula: Pressure = Force / Area
Pressure decreases if the area increases.

Archimedes’ Principle:
When a body is immersed in a fluid, it experiences an upward force equal to the weight of the fluid displaced by it. This explains why some objects float and others sink.

Relative Density:
Relative density is the ratio of the density of a substance to the density of water.
Formula: Relative Density = Density of substance / Density of water.