# Fundamental Concepts in Classical Physics

1. Gravity

Gravity is the force that keeps us grounded and attached to the earth. It pulls everything towards the center of the earth, including people, planets, stars, and even atoms. Without gravity, we would float around freely in space. Gravity is what makes our planet Earth stay in orbit around the sun.

2. Centripetal Force

Centripetal force is the force that causes objects to move toward the center of mass. When an object moves in a circle, it experiences centripetal force. If you throw a ball straight up in the air, it will fall back down to the ground due to the force of gravity pulling it back to the earth.

3. Gravitational Potential Energy

Gravitational potential energy is the energy that comes from the gravitational field of a body. A body's gravitational potential energy is equal to its weight (mass) times the height of the body above the surface of the earth.

4. Inertia

Inertia is the property of matter that resists changes in motion. Objects have inertia because they continue moving until acted upon by an outside force. An example of inertia is a bowling ball rolling down a hill. As long as the ball is not acted upon by any external forces, it continues to roll downhill.

5. Newton's Laws

Newton's laws are three fundamental physical principles that govern how things behave in the universe. These laws explain many phenomena, including gravity, acceleration, momentum, and conservation of energy.

6. Conservation of Momentum

Conservation of momentum states that if an object is at rest, then it cannot change speed without some kind of force acting on it. If an object is moving, it will keep moving unless something stops it.

7. Law of Universal Gravitation

The law of universal gravitation states that two massive bodies attract each other with a force directly proportional to their masses and inversely proportional to the square of the distance between them.