Glossary
Acceleration
The rate at which an object's velocity changes over time, involving changes in speed, direction, or both.
Example:
A car speeding up from a stop sign is undergoing positive acceleration.
Action-Reaction Pair
Two forces that are equal in magnitude and opposite in direction, acting on different interacting objects, as described by Newton's Third Law.
Example:
When you push against a wall, the force you exert on the wall and the force the wall exerts back on you form an action-reaction pair.
Benjamin Franklin
An American polymath known for his extensive experiments with electricity, including identifying positive and negative charges and inventing the lightning rod.
Example:
Benjamin Franklin's kite experiment famously showed that lightning is a form of electricity.
Charge (q)
A fundamental property of matter that causes it to experience a force when placed in an electromagnetic field.
Example:
Electrons carry a negative charge, while protons carry a positive charge.
Charles-Augustin de Coulomb
A French physicist who established the quantitative law of electric force, now known as Coulomb's Law.
Example:
Charles-Augustin de Coulomb's torsion balance experiment allowed him to precisely measure the forces between electric charges.
Coulomb (C)
The SI unit of electric charge, defined as the amount of charge transported by a constant current of one ampere in one second.
Example:
A typical lightning bolt can transfer several Coulombs of charge.
Coulomb's Constant (k)
A proportionality constant in Coulomb's Law, with a value of approximately $8.99 imes 10^9 N m^2/C^2$, relating the electric force to charges and distance.
Example:
The magnitude of the electric force is significantly large due to the high value of Coulomb's Constant.
Coulomb's Law
A fundamental law stating that the electric force between two point charges is directly proportional to the product of their charges and inversely proportional to the square of the distance between them.
Example:
Using Coulomb's Law, physicists can calculate the strong repulsive force between two protons in an atomic nucleus.
Electric Forces
Fundamental forces that arise between electrically charged particles, which can be either attractive or repulsive.
Example:
The reason a balloon rubbed on hair can stick to a wall is due to electric forces.
Forces
Interactions that can cause a change in an object's state of motion, either by starting, stopping, or changing its direction or speed.
Example:
When you push a shopping cart, you apply a force that causes it to accelerate.
Gravitational Force
The attractive force between two objects due to their masses, calculated using Newton's Law of Universal Gravitation.
Example:
The gravitational force between you and the Earth is what gives you weight.
Gravitational Mass
A measure of an object's response to a gravitational field, determining the strength of the gravitational force it experiences.
Example:
On the Moon, an astronaut's gravitational mass remains the same as on Earth, even though their weight is less.
Gravity
A fundamental force of attraction between any two objects with mass, always attractive and following an inverse square law.
Example:
The Earth's gravity keeps the Moon in orbit around it.
Inertia
The inherent tendency of an object to resist changes in its state of motion, whether it is at rest or moving at a constant velocity.
Example:
When a car suddenly brakes, your body continues to move forward due to inertia.
Inertial Mass
A measure of an object's resistance to acceleration when a net force is applied, representing the mass that is accelerated.
Example:
A bowling ball has greater inertial mass than a tennis ball, making it harder to accelerate with the same force.
Inverse Square Law
A physical law stating that a specified physical quantity or intensity is inversely proportional to the square of the distance from the source of that physical quantity.
Example:
Both gravity and electric force follow an inverse square law, meaning their strength rapidly diminishes with increasing distance.
Kilogram (kg)
The SI base unit of mass, used to quantify the amount of matter in an object.
Example:
A standard bag of sugar typically has a kilogram of mass.
Mass
A fundamental property of matter that quantifies its inertia and its resistance to changes in motion.
Example:
A kilogram of feathers has the same mass as a kilogram of lead, despite their different volumes.
Meters per second squared (m/s²)
The SI unit of acceleration, representing the change in velocity per unit time.
Example:
The acceleration due to gravity near Earth's surface is approximately 9.8 meters per second squared.
Net Force
The vector sum of all individual forces acting on an object, determining its overall acceleration.
Example:
If you push a box with 10 N to the right and a friend pushes with 5 N to the left, the net force on the box is 5 N to the right.
Newton (N)
The SI unit of force, defined as the force required to accelerate a mass of one kilogram at a rate of one meter per second squared.
Example:
A small apple weighs approximately 1 Newton.
Newton's First Law
Also known as the Law of Inertia, it states that an object at rest stays at rest, and an object in motion stays in motion with the same velocity unless acted upon by a net external force.
Example:
A soccer ball sitting motionless on the field will remain at rest until a player kicks it, demonstrating Newton's First Law.
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, expressed by the formula F=ma.
Example:
Pushing a lighter box with the same force as a heavier box will result in the lighter box having greater acceleration, illustrating Newton's Second Law.
Newton's Third Law
States that for every action, there is an equal and opposite reaction, meaning forces always occur in pairs acting on different objects.
Example:
When a rocket expels hot gas downwards, the gas exerts an equal and opposite upward force on the rocket, demonstrating Newton's Third Law.
Triboelectricity
The phenomenon where electric charge is generated by friction between two different materials, often resulting in static electricity.
Example:
Rubbing a comb through your hair and then picking up small pieces of paper demonstrates triboelectricity.
Vectors
Physical quantities that have both magnitude (size) and direction, such as force, velocity, and acceleration.
Example:
When describing wind, stating it's blowing at 20 km/h to the east makes it a vector quantity.