Gravitation: Introduction and Newton's Laws

Vocabulary flashcards covering the discovery and nature of gravitation, Earth's gravitational pull, and Newton's three laws of motion.

Gravitational force

A universal attractive force that acts not only between two objects on the Earth but also between any two objects in the universe.

Sir Isaac Newton

The scientist who discovered the phenomenon of gravitation after observing an apple fall vertically downward from a tree toward the ground.

Direction of Earth's gravitational force

Directed towards the center of the Earth, which corresponds to the vertical direction along the perpendicular from the position of an object to the surface of the Earth.

Figure 1.1: Concept of gravitational force

A diagram illustrating the attractive force on a falling apple directed towards the center of the Earth and the gravitational force between the Earth and the Moon.

Force (in motion)

An agency necessary to change both the speed as well as the direction of motion of an object.

Newton's First Law of Motion

An object continues to be at rest or in a uniform motion unless an external unbalanced force acts on it.

Newton's Second Law of Motion

The rate of change of momentum is directly proportional to the applied force, and the change of momentum takes place in the direction of the applied force.

Newton's Third Law of Motion

Every action has an equal and opposite reaction.