- acceleration — The time rate of change of velocity of an object, or alternately the net force on the object divided by the object's mass.
- amplitude — The magnitude of the maximum displacement from the rest position of an oscillating system.
- angular acceleration — The rate of change of the angular velocity with time, or the second derivative of the angular position with respect to time. For systems rotating about a single axis with a fixed moment of inertia about that axis, the angular acceleration is directly proportional to the net torque acting on the system.
- angular frequency — The magnitude of the angular velocity vector, ω. An angular frequency can also be defined for periodic linear motions like Simple Harmonic Motion by multiplying the ordinary frequency f by 2π (ω = 2πf).
- angular impulse — the angular impulse is the integral of torque (single-axis) over the time it acts.
- angular momentum about a single axis — The circulation of linear momentum about the specified axis, being proportional to the component of momentum or each mass along a circle about the axis and the radius of the circle. Angular momentum is changed by external torques, and therefore is constant when these sum to zero. The angular momentum of a rigid body is proportional to its moment of inertia times its angular velocity.
- angular position — The angular coordinate of a location in polar coordinates, generally represented by the small Greek letter theta, θ .
- angular velocity — The change in angular position with time, the angular analogue of linear velocity. It is a vector, having both magnitude and direction. In introductory mechanics we will almost always deal with cases of angular velocity about a single axis of rotation, so that the angular velocity is confined to one dimension.
- axis of rotation — An imaginary line chosen by the problem solver that is perpendicular to the plane of motion of a system and about which angular momenta and torques are calculated.
- center of mass — The average position of the mass in a body or system. A system will behave in response to external forces applied to any of its parts as if the entire mass of the body were concentrated there. The motion of the center of mass is unaffected by internal forces in the system (e.g. forces between the atoms, or collisions between different components of the system).
- centripetal acceleration — The acceleration directed toward the center of rotation that results from the change in direction (not magnitude) of the velocity when an object is in circular motion.
- coefficient of friction — Actually two different, but related, constants of proportionality, relating frictional force to the associated normal force
- conservative force — A force which has an associated potential energy. In introductory mechanics, the only conservative forces generally encountered are gravitation (universal) and elastic forces which satisfy Hooke's Law for elastic interactions.
- conserved — A quantity that is constant in time (does not change) is said to be conserved.
- coordinate system — A set of mathematical axes which serve as a quantitative map grid, allowing precise specification of positions of objects. Cartesian coordinates are most common in introductory mechanics, but cylindrical coordinates are sometimes useful, especially for circular or orbital motion.
- cross product — Also known as the vector product, the cross product is a way of multiplying two vectors to yield another vector.
- decomposition — Decomposing a problem into parts, each amenable to solution using the S.I.M. approach.
- Delta-v diagram — A graphical approach to understanding the form of the centripetal acceleration.
- displacement — change in position of an object from a fixed reference point.
- distance — distance is a scalar measurement of the change in location of something from a fixed reference point. It differs from the displacement, which is a vector measurement of the change in location.
- dot product — A common term for the scalar product, since the scalar product is symbolically indicated by placing a dot between the two vectors being multiplied
- dynamics — The branch of mechanics that is the study of the interplay between the applied forces on a mechanical body and the resulting motion.
- elastic collision — A collision in which the momentum and kinetic energy of the system consisting of all objects participating in the collision remains constant.
- elementary fermionic particle — Thought to be the building blocks of all matter, the fermionic particles currently believed to be elementary (indivisible) are quarks and leptons.
- environment — The things that can interact with a system and influence its behavior, but which are not directly part of the system and are not modeled.
- equilibrium position — A stable position in which all forces are balanced (vector sum is zero) and the object of interest is not in motion. Equilibria may be stable or unstable depending on whether the force acts back toward or away from the equilibrium position if the particle is slightly displaced from in.
- experiment — Careful observations of constructed situations that have the ability to falsify Laws, measure parameters of the laws, or properties of physical objects.
- external force — A force exerted on a constituent of a system by the environment.
- fixed axis — A situation in which the axis of rotation is physically constrained to be in a set location relative to the moving parts, usually because it is fabricated as an axle.
- force — Force produces a change in the momentum of a mass on which it acts, according to F=ma (Newton's Second Law). Forces result from various types of physical interactions, which always generate a pair of opposite forces acting on two different objects (Newton's Third Law).
- force diagram — a schematic drawing showing the object under consideration (often represented as a point mass) and the forces acting upon it. the forces are represented as vectors and are labeled.
- free body diagram — A graphical representation used to analyze the forces exerted on a single system by its environment.
- freefall — An object that is subject only to the force of gravity is in freefall.
- friction (interaction)
- fundamental forces — Forces which can influence the motion of at least one class of elementary fermionic particle. The only fundamental force which is studied directly in introductory mechanics is gravity.
- gee — gee , or g , is a measure of acceleration equal to the acceleration due to gravity (interaction) at the earth's surface.
- gravity (interaction)
- gyroscope — A rapidly-spinning symmetrical top usually used to maintain direction or to demonstrate the principles of angular momentum. Often one treats it with the "gyroscopic approximation" which assumes that the angular momentum is parallel to the direction of spin (i.e. the contribution from precession is assumed negligible).