Newton

Isaac Newton developed a unified conceptual framework for physics and orbital mechanics, published in his 1687 work Philosophiae Naturalis Principia Mathematica.

Newton’s Laws of Motion

• Newton’s First Law (Law of Inertia)

  • An object remains at rest or continues moving at a constant velocity in a straight line unless acted upon by an outside force.

  • Momentum is defined as mass times velocity ($\text{momentum} = \text{mass} \times \text{velocity}$) and is conserved in the absence of external forces.

• Newton’s Second Law (Force and Acceleration)

  • Force causes a change in momentum over time.

  • Applied force produces acceleration proportional to the force and inversely proportional to the object's mass.

• Newton’s Third Law (Action and Reaction)

  • For every action, there is an equal and opposite reaction.

  • Forces always occur in equal and opposite pairs (e.g., rocket propulsion, recoil, gravitational pull).

Mass, Volume, and Density

• Mass: Measure of the total amount of matter in an object.

• Volume: Physical space occupied by an object.

• Density: Ratio of mass to volume ($\text{density} = \frac{\text{mass}}{\text{volume}}$), typically expressed in units such as $g\,cm^{-3}$.

Angular Momentum

• Angular Momentum: Measure of rotational motion around a fixed point, defined as $\text{angular momentum} = \text{mass} \times \text{velocity} \times \text{distance}$.

• Conservation of Angular Momentum: Total angular momentum remains constant unless acted on by external influences. As distance to the center of rotation decreases, rotational speed increases (e.g., Kepler's second law