Glossary
Action at a Distance
The concept that a force can be exerted on an object without any physical contact between the interacting bodies.
Example:
The Earth's gravity pulling on the Moon, despite the vast emptiness of space between them, is an example of action at a distance.
Attractive (Force)
A type of force that pulls two objects towards each other.
Example:
The force between a proton and an electron is attractive, pulling them together.
Coulomb's Law
A law describing the electrostatic force between two charged particles, stating it 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, you can calculate the exact force between two charged spheres, like those in the free-response problem.
Electric Charge
A fundamental property of matter that causes it to experience a force when placed in an electromagnetic field, and to create such a field.
Example:
An electron carries a negative electric charge, while a proton carries a positive one.
Electric Force
The fundamental force between charged particles, which can be either attractive (between opposite charges) or repulsive (between like charges).
Example:
The attraction between a positively charged glass rod and a negatively charged plastic comb is an electric force.
Electromagnetic Forces
Fundamental forces arising from the interaction of charged particles, encompassing both electric and magnetic phenomena.
Example:
The force that holds electrons in orbit around an atomic nucleus is an electromagnetic force.
Fields
Regions of space where a force would be exerted on a suitable object, such as a mass in a gravitational field or a charge in an electric field.
Example:
A magnet creates a magnetic field around it, which can exert a force on other magnetic materials or moving charges.
Gravitational Force
The attractive force between any two objects with mass, proportional to the product of their masses and inversely proportional to the square of the distance between their centers.
Example:
The reason an apple falls from a tree to the ground is due to the gravitational force between the apple and the Earth.
Inverse Square Law
A principle stating that the strength of a physical quantity, such as force or intensity, is inversely proportional to the square of the distance from the source.
Example:
If you double the distance from a light source, the intensity of the light you receive decreases by a factor of four, illustrating the inverse square law.
Magnetic Force
A force exerted on moving electric charges or currents in a magnetic field, whose direction depends on the velocity of the charge and the magnetic field direction.
Example:
A compass needle aligns itself with Earth's magnetic field due to the magnetic force acting on its tiny internal magnets.
Magnitude of Charges
The absolute value of the electric charge on a particle or object, which directly affects the strength of the electric force it exerts or experiences.
Example:
Two balloons rubbed vigorously will have a larger magnitude of charges and thus experience a stronger repulsive electric force when brought near each other.
Mass
A fundamental property of matter that quantifies its inertia and is the source of gravitational force.
Example:
A bowling ball has significantly more mass than a tennis ball, which is why it's harder to accelerate and exerts a stronger gravitational pull.
Motion of Charged Objects
The movement of electrically charged particles, which is a prerequisite for the existence of magnetic forces.
Example:
A current flowing through a wire, which is the motion of charged objects (electrons), creates a magnetic field around it.
Potential Lines
Imaginary lines or surfaces in a force field where the potential energy is constant, used to visualize the field's characteristics.
Example:
In a topographic map, contour lines represent constant elevation, similar to how potential lines represent constant electric potential in an electric field.
Repulsive (Force)
A type of force that pushes two objects away from each other.
Example:
When you try to push the north poles of two magnets together, you feel a repulsive force.
Spatial Scale
Refers to the distance between interacting objects, which significantly influences the strength of gravitational and electromagnetic forces.
Example:
The vast spatial scale between Earth and Mars means the gravitational pull between them is much weaker than between Earth and a nearby satellite.