Glossary
Equilibrium
The state of an object when the net force acting on it is zero. The object will either remain at rest or continue moving at a constant velocity.
Example:
A book resting on a table is in equilibrium because the upward normal force balances the downward gravitational force.
Frame of Reference
A coordinate system from which motion is observed. It provides the viewpoint for analyzing an object's movement.
Example:
Observing a ball dropped inside a moving train from the perspective of someone standing on the platform requires considering different frames of reference.
Gravitational Force
The attractive force between any two objects with mass, commonly experienced as weight near a planet. It is calculated as mass times the acceleration due to gravity (F=mg).
Example:
The gravitational force acting on a 1 kg object near Earth's surface is approximately 9.8 Newtons, pulling it downwards.
Gravitational Mass
A measure of how strongly an object is attracted to other objects due to gravity. It determines the gravitational force an object experiences.
Example:
When you step on a bathroom scale, it measures your gravitational mass by determining the force of gravity acting on you.
Inertia
The tendency of an object to resist changes in its state of motion. It's an object's 'laziness' to speed up, slow down, or change direction.
Example:
It's much harder to push a stalled truck than a bicycle because the truck has significantly more inertia.
Inertial Frame of Reference
A frame of reference that is not accelerating, meaning it is either at rest or moving at a constant velocity. Newton's laws are valid in these frames.
Example:
A person standing still on the ground is in an inertial frame of reference, while someone on a spinning merry-go-round is not.
Inertial Mass
A quantitative measure of an object's resistance to changes in its state of motion (acceleration). The more inertial mass an object has, the harder it is to accelerate.
Example:
A bowling ball has a much greater inertial mass than a tennis ball, which is why it takes more force to get the bowling ball rolling at the same speed.
Mass
A fundamental property of matter that quantifies both an object's inertia (resistance to acceleration) and its gravitational attraction. It is a scalar quantity.
Example:
Whether you're on Earth or the Moon, your mass remains the same, even though your weight would change.
Newton's First Law
An object at rest stays at rest, and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force.
Example:
When a car suddenly brakes, your body continues to move forward due to Newton's First Law, trying to maintain its original motion.
Newton's Second Law
States that the acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass (F=ma). It quantifies the relationship between force, mass, and acceleration.
Example:
Pushing a shopping cart with a constant force causes it to accelerate, and if you double the force, the acceleration will also double according to Newton's Second Law.
Weight
The force of gravity acting on an object, calculated as the product of its mass and the acceleration due to gravity (W=mg). It is a vector quantity.
Example:
An astronaut's weight on the Moon is significantly less than on Earth, even though their mass is unchanged.