Frame of Reference
Any measurements of position, distance, or speed must be made with respect a reference frame or frame of reference.
Displacement
The change in position of the object from its starting point.
Average Speed
The total distance traveled along its path divided by the time it takes to travel that distance.
Velocity
The magnitude of how fast an object is moving and also the direction in which it is moving.
Average Velocity
The displacement divided by the elapsed time.
Elapsed Time or Time Interval
The time that has passed during our chosen period of observation.
Instantaneous Velocity
The average velocity during an infinitesimally short time interval.
Average Acceleration
The change in velocity divided by the time taken to make this change.
Instantaneous Acceleration
The average acceleration during infinitesimally short time interval.
Decelerate
The magnitude of the velocity is decreasing. (It does not mean it is negative.)
Acceleration Due to Gravity
At a given location on the Earth and in the absence of air resistance, all objects fall with the same constant acceleration.
Slope of a Line
The change in the dependent variable divided by the corresponding change in the independent variable.
Slope of a Curve
The slope of the tangent to the curve at that point. (A straight line drawn so it touches the curve only at that one point.)
Resultant
The arrow drawn from the tail of the first vector to the tip of the second vector represents the sum.
Relative Velocity
The velocity of an object relative to one frame of reference can be found by vector addition if its velocity relative to a second frame of reference are known.
Force
A push or pull on an object.
Newton's First Law of Motion
Every object continues in its state of rest, or uniform velocity in a straight line, as long as no net force acts on it.
Inertia
The tendency of an object to maintain its state of rest or uniform motion in a straight line.
Law of Inertia
(Another name for Newton's First Law of Motion) Every object continues in its state of rest, or uniform velocity in a straight lone, as long as no net force acts on it.
Inertial Reference Frames
Reference frames in which Newton's First Law holds.
Non-inertial Reference Frames
Reference frames where Newton's First Law does not hold, such as accelerating reference frames.
Mass
A measure of the inertia of an object.
Weight
The magnitude of the force of gravity (gravitational force) on an object.
Newton's Second Law of Motion
The acceleration of an object is directly proportional to the net force acting on it, and is inversely proportional to its mass. The direction of the acceleration is in the direction of the net force acting on the object.
Net Force
The vector sum of all forces on the object.
Force
An action capable of accelerating an object.
Newton (N)
Unit of force.
Newton's Third Law of Motion
Whenever one object exerts a force on a second object, the second exerts an equal force in the opposite direction on the first.
Normal Force
When a contact force acts perpendicular to the common surface of contact.
Contact Force
The for exerted by the surface.
Free-Body Diagram
A diagram showing all the forces acting on each object involved.
Tension
When a flexible cord pulls on an object creates the force tension.
Kinetic Friction
When an object slides along a rough surface, the force of kinetic friction (sliding friction) acts opposite to the direction of the object's velocity.