Glossary
Acceleration Due to Gravity (g)
The acceleration experienced by an object due to the gravitational pull of a massive body, which varies with distance from the center of the body.
Example:
While on Earth's surface, the acceleration due to gravity (g) is approximately , it is significantly less on Mars.
Air Resistance
A type of frictional force that opposes the motion of an object through the air, dependent on factors like speed, shape, and air density.
Example:
Air resistance is why a crumpled piece of paper falls faster than a flat sheet of the same paper.
Attractive (Gravitational Force)
Describes the inherent nature of gravity, meaning it always pulls objects towards each other, never repelling them.
Example:
The attractive nature of gravity is why objects fall towards the Earth's surface rather than floating away.
Conservative Force (Gravity)
A force for which the work done in moving an object between two points is independent of the path taken, and the total work done on a closed path is zero.
Example:
Because gravity is a conservative force, the energy required to lift a rocket to a certain height is the same regardless of the path it takes.
Distance (Inverse Square Dependence)
The separation between the centers of two masses, where the gravitational force decreases proportionally to the square of this distance.
Example:
If a satellite doubles its distance from Earth, the gravitational force on it becomes one-fourth as strong due to the inverse square law.
Gravitational Constant (G)
A fundamental physical constant that quantifies the strength of the gravitational force. Its approximate value is $6.67 \times 10^{-11} \frac{N \cdot m^2}{kg^2}$.
Example:
The gravitational constant (G) is a universal value, meaning it's the same whether you're calculating forces on Earth or in deep space.
Gravitational Field
A region of space surrounding a massive object within which another massive object experiences a force of attraction.
Example:
The Earth creates a gravitational field that keeps the Moon in orbit around it.
Long-Range Force
A force that acts over vast distances, responsible for phenomena like planetary orbits, the motion of galaxies, and the large-scale structure of the universe.
Example:
Gravity is a long-range force, which is why the Sun's gravitational pull can influence planets billions of kilometers away.
Newton's Law of Universal Gravitation
States that every object attracts every other object in the universe with a force directly proportional to the product of their masses and inversely proportional to the square of the distance between their centers.
Example:
Using Newton's Law of Universal Gravitation, scientists can predict the precise orbital paths of planets and spacecraft.
Newton's Third Law (Gravitation)
States that the gravitational force exerted by object A on object B is equal in magnitude and opposite in direction to the force exerted by object B on object A.
Example:
The Earth pulls on the Moon with the same force that the Moon pulls on the Earth, perfectly illustrating Newton's Third Law in action.
Product of the Masses
Refers to the multiplication of the masses of the two interacting objects, which directly determines the magnitude of the gravitational force between them.
Example:
The gravitational force between a star and a planet is directly proportional to the product of the masses of both celestial bodies.
Terminal Velocity
The constant speed that a freely falling object eventually reaches when the resistance of the medium through which it is falling prevents further acceleration.
Example:
A skydiver reaches terminal velocity when the upward force of air resistance perfectly balances the downward force of gravity.
Variable Gravitational Force
The concept that the gravitational force acting on an object changes as its distance from the source of gravity changes, specifically decreasing with increasing distance.
Example:
As a space probe travels from Earth to Jupiter, it experiences a variable gravitational force that changes in magnitude and direction.