Lecture Notes: Gravitation

Introduction

The lecture explores the chapter on gravitation, focusing on the gravitational pull or gravitational force.
Emphasis on the Universal Law of Gravitation.

The Moon revolves around the Earth due to centripetal force
- Centripetal force is a type of gravitational force.
Despite Earth's attraction, the Moon does not fall into Earth.
- It orbits Earth in an elliptical (almost circular) path.
- At every moment, the Moon misses the chance to fall into Earth.
Example Explanation: Like rotating a tied chalk piece, where the string provides the centripetal force.

Definition: An object falls towards Earth only due to gravitational force.
Key Point: Free fall occurs when gravity is the sole force acting upon the object.
Demonstration: A stone falls faster than paper due to air resistance affecting lighter objects.
- Air resistance acts as a push against gravity, affecting lighter objects more.
In Vacuum: Without air resistance (e.g., in a glass chamber), objects fall at the same rate regardless of mass.

As an object falls, it experiences acceleration due to gravitational force.
Acceleration due to gravity (g): 9.8 m/s².
Formula:
- Gravitational force causes acceleration (F = mg)
- Derived Formula for g: ( g = \frac{GM}{R^2} )
  - G = Gravitational constant
  - M = Mass of Earth
  - R = Radius of Earth
Variations in g:
- Equator: Larger radius, smaller g value
- Poles: Smaller radius, larger g value

Equations of Motion: Adapted for gravitational influence.
- ( v = u + gt )
- ( s = ut + \frac{1}{2}gt^2 )
- ( v^2 = u^2 + 2gs )
Sign of g:
- Positive (9.8 m/s²) when the object is falling down.
- Negative (-9.8 m/s²) when the object is moving up.
Note: Height (h) may substitute for distance (s) in some calculations.

Understanding the principles of gravitation is fundamental.
Future topics include problems on universal law of gravity and motion under gravity.
Encouragement to like and share the video for wider reach and motivation.