Chapter 5: Gravity

Newton’s 3 Laws of Motion

Newton’s 3 Laws of Motion

1. Law of Inertia: Objects at rest stay at rest, and objects in motion stay in motion unless acted upon by an external force.

2. Law of Acceleration: F = ma, stating that force equals mass times acceleration.

3. Law of Action-Reaction: For every action, there is an equal and opposite reaction.

Force of Gravity

Force that attracts objects towards each other. It is directly proportional to the product of their masses and inversely proportional to the square of the distance between their centers.

Orbital Velocity

The constant speed an object must maintain to stay in orbit around a celestial body, balancing the gravitational pull with the object's inertia.

Escape Velocity

the minimum speed an object must reach to break free from a gravitational field without further propulsion.

First Postulate of Relativity

the laws of physics are the same in all inertial frames of reference. Speed of light is constant and independent of the motion of the source.

Second Postulate of Relativity

the speed of light in a vacuum is constant for all observers, regardless of the motion of the light source or the observer.

Third Postulate of Relativity

observers cannot distinguish locally between inertial forces due to acceleration and uniform gravitational forces due to the presence of a massive body

Newton’s Version of KP’s 3rd Law

P²=(4pi²r³)/GM