Acceleration: The rate of change
of an object's velocity with respect to time. Also,
change in velocity divided by the time interval over
which it occurred.
Air Density: Density is defined in a qualitative
manner as the measure of the relative "heaviness"
of objects with a constant volume. Ratio of an air
sample's mass to its volume.
Air Resistance (also Air Drag and Drag): A
resistive (frictional) force, which is the result
of a moving object colliding with air molecules.
Boundary Layer: The stable layer of air on
the leading surface of an object moving through the
air.
Center of Mass: 1. The point in a system of
bodies or an extended body at which the mass of the
system may be considered to be concentrated and at
which external forces may be considered to be applied.
2. Point representing the mean position of the matter
in a body.
Coefficient of Restitution (COR): The
ratio of the velocity of an object rebounding from
the surface of a hard, immovable object to its incident
velocity. The coefficient of restitution is used to
measure the elasticity of the collision between two
objects (for example: a baseball and a bat).
Conservation of Energy: Principle stating
that energy can be converted from one form into another
but it cannot be destroyed or created; the total amount
of energy remains constant.
Drag Coefficient: A measure of the aerodynamic
sleekness of an object. Drag coefficient is signified
by (C_{d}). The lower the number, the greater
the aerodynamic efficiency.
Dynamics: The branch of physics concerned
with the study of motion.
Elastic Collision: A collision in which objects
rebound from each other with negligible loss of kinetic
energy.
Elastic Potential Energy: Energy that is due
to compression or deformation of an elastic material
such as a spring.
Energy: The capacity for doing work or causing
changes in matter.
Force: A physical quantity that results in
accelerating or deforming an object.
Friction: A force that resists the relative
motion of objects that are in contact with each other.
Gravitational Acceleration: At the earth's
surface all objects with mass accelerate downward
at the rate of g = 9.8 m/s^{2} (32 ft. per
sec per sec).
Heat Energy: A form of energy representing
the kinetic energy of atoms and molecules in an object.
Humidity: The measure of the amount of water
vapor contained in a sample of air.
Inelastic Collision: A collision in which
the colliding objects stick together after impact.
Inertia: The property of matter that causes
it to resist any change in its motion. An object's
inertia is directly proportional to its mass.
Kinematics: The part of dynamics that describes
motion without regard to its causes.
Kinetic Energy: Energy possessed by an object
because of its motion.
Magnus Effect, The: The Magnus effect is the
name given to the physical phenomenon whereby an object's
rotation affects its path through a state of matter,
in particular, air. The perpendicular force associated
with the change in path is commonly referred to as
the Magnus force.
Mass: A measure of the quantity of matter
in an object; its inertia or resistance to change
in motion.
Momentum: The product of the mass and velocity
of a moving body.
Net Force: The vector sum of all forces acting
upon an object.
Newton's Three Laws of Motion

Newton's First Law of Motion: A body at
rest or in uniform motion in a straight line will
remain at rest or in the same uniform motion unless
acted upon by an external force; also called the
law of inertia.

·Newton's Second Law of Motion: The
acceleration of a body is directly proportional
to the net force exerted on the body, is inversely
proportional to the mass of the body, and has
the same direction as the net force; also called
the law of acceleration.

Newton's Third Law of Motion: If one body
exerts a force on a second body, then the second
body exerts a force equal in magnitude and opposite
in direction on the first body; also called the
law of interaction.
Parabolic: The shape of a projectile's trajectory,
neglecting air resistance.
Pressure: Force per unit area.
Projectile Motion: Any object moving freely
through the air without the aid of any sort of propulsion
system. A typical example would be a thrown object
(javelin, shot put, baseball).
Resultant Vector: A single vector that represents
the sum total of several component vector quantities.
Rotational Velocity: Time rate of change of
an object's angular position. It is commonly defined
in terms of the number of revolutions the object makes
in a given time period (i.e., RPM or revolutions per
minute).
Smooth Air Flow: Airflow that is primarily
in one direction; sometimes called laminar flow.
Speed: Rate of change of an object's position.
Temperature: The average kinetic energy of
atoms and molecules in an object.
Trajectory: The path of a projectile or other
moving body through space.
Turbulent Air Flow: Airflow that is smooth,
or laminar, in nature. Evidenced by swirling, multidirectional
airflow patterns.
Vector: A quantity in which both the magnitude
and the direction must be stated. Force, velocity
and field strength are examples of vector quantities.
Distance and speed are scalar quantities but displacement
and velocity are vector quantities.
Velocity: Speed in a specified direction.
