Glossary
Acceleration
The rate at which an object's velocity changes over time, which can involve a change in speed, direction, or both.
Example:
When a car slams on its brakes, it experiences negative acceleration, causing it to slow down.
Action-Reaction Pairs
Two forces that are equal in magnitude and opposite in direction, acting on different interacting objects, as described by Newton's Third Law.
Example:
The force of Earth pulling on the Moon and the force of the Moon pulling on Earth form an action-reaction pair.
Charged Particles
Subatomic particles (like electrons and protons) or macroscopic objects that possess a net electric charge, either positive or negative.
Example:
In a cathode ray tube, a beam of charged particles (electrons) creates the image on the screen.
Coordinate System
A framework, typically with perpendicular axes (like x and y), used to define the position and direction of forces and motion.
Example:
When analyzing projectile motion, using a coordinate system with the x-axis horizontal and the y-axis vertical simplifies calculations.
Coulomb's Law
Describes the electrostatic force between two point charges, stating it is directly proportional to the product of their magnitudes and inversely proportional to the square of the distance between them.
Example:
Coulomb's Law explains why two positively charged balloons repel each other more strongly when they are closer together.
Direction
The orientation or path along which a vector quantity acts, typically specified by an angle or cardinal points.
Example:
When navigating, knowing the direction (e.g., north, 45 degrees east of north) is as crucial as knowing the distance.
Electric Field
A region around a charged particle or object where a force would be exerted on other charged particles.
Example:
A Van de Graaff generator creates a strong electric field around its dome, causing hair to stand on end.
Electromagnetic Forces
Fundamental forces arising from the interaction of electrically charged particles, responsible for phenomena like electricity, magnetism, and light.
Example:
The static cling that makes clothes stick together after drying is due to electromagnetic forces.
Forces
Interactions between objects that can cause a change in an object's motion or shape.
Example:
When a soccer player kicks a ball, they apply a force to it, causing it to accelerate across the field.
Free-Body Diagrams
Visual representations that isolate an object and show all external forces acting *on* it as labeled arrows originating from the object.
Example:
Before solving a complex problem involving a car on a ramp, drawing a free-body diagram helps identify all the forces at play.
Inertial Reference Frames
Reference frames in which an object at rest remains at rest, and an object in motion continues in motion with constant velocity, unless acted upon by a net force.
Example:
A smoothly gliding spaceship in deep space can be considered an inertial reference frame where objects float without external forces.
Magnetic Field
A region around a moving electric charge or a magnetic material where a magnetic force can be observed.
Example:
A compass needle aligns itself with the Earth's magnetic field, pointing towards the magnetic north pole.
Magnitude
The numerical value or size of a vector quantity, indicating its strength or extent.
Example:
The speedometer in a car shows the magnitude of its velocity, but not its direction.
Net Force
The vector sum of all individual forces acting on an object, determining its acceleration.
Example:
If two people push a box with equal force in opposite directions, the net force on the box is zero, and it won't move.
Newton's Third Law
States that for every action, there is an equal and opposite reaction; forces always occur in pairs acting on different objects.
Example:
When a swimmer pushes water backward, the water pushes the swimmer forward, illustrating Newton's Third Law.
Newtons (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 typically weighs about 1 Newton on Earth.
Vectors
Physical quantities that possess both magnitude (size) and direction.
Example:
To describe the wind, you need to know both its speed (magnitude) and its direction, making wind velocity a vector quantity.