Glossary
Acceleration Due to Gravity (g)
The constant acceleration experienced by all objects falling freely near the surface of a celestial body, independent of their mass (in a vacuum). On Earth, its approximate value is 9.8 m/s².
Example:
When you drop a ball, it speeds up at 9.8 m/s² due to the Earth's acceleration due to gravity.
Conservation of Mass
A fundamental principle stating that the total amount of mass in a closed system remains constant over time; mass cannot be created or destroyed, only transformed.
Example:
When ice melts into water, the total mass of the H₂O remains the same, illustrating the conservation of mass.
Equivalence Principle
The fundamental concept that inertial mass and gravitational mass are experimentally found to be equal, implying that all objects fall at the same rate in a vacuum regardless of their mass.
Example:
The Apollo 15 experiment, where a hammer and feather fell simultaneously on the Moon, beautifully demonstrated the Equivalence Principle.
Gravitational Force
The attractive force between any two objects with mass, responsible for phenomena like objects falling to Earth and planetary orbits.
Example:
The gravitational force between the Earth and the Moon keeps the Moon in its orbit.
Gravitational Mass
A measure of how strongly an object interacts with gravity, determining the amount of gravitational force it experiences in a gravitational field.
Example:
A massive star has a large gravitational mass, causing a strong pull on nearby planets.
Inertial Mass
A measure of an object's resistance to changes in its state of motion (acceleration). The greater the inertial mass, the more force is required to accelerate the object.
Example:
It takes a lot more force to push a car than a bicycle because the car has much greater inertial mass.
Newton's Law of Universal Gravitation
A fundamental law describing the attractive gravitational force between two masses, 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, you can calculate the force pulling a satellite towards Earth.
Newton's Second Law
A fundamental law stating that the net force acting on an object is equal to the product of its inertial mass and its acceleration (F=ma).
Example:
When a soccer player kicks a ball, Newton's Second Law explains how the force of the kick determines the ball's acceleration.