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Based on the newest Paul Hewitt conceptual physics textbook, published 2009

Scientific methods

effective in gaining, organizing, and applying new knowledge


close agreement by competent observers who make a series of observations of the same phenonmenon


educated guess that is not fully accepted until demonstrated by experiment

Laws or Principles

when hypotheses about the relationship among natural quantities are tested over and over again and not contradicted, may become...


a synthesis of a large body of information that encompasses well-tested and verified hypotheses about certain aspects of the natural world


a push or pull

net force

combination of all forces acting on an object




an arrow that represents the magnitued and direction of a quantity

vector quantity

quantity that needs both magnitude and direction for a complete description (Ex: force)

scalar quanity

quantity that can be described by magnitude only and has no direction (Ex: time, area, and volume)

Mechanical equilibrium

state wherein no physical changes occur

Equilibrium rule

whenever the net force on an object is zero the object is said to be in mechanical equilibrium

Support force

the upward force that balances the weight of an object on a surface


the sum of two or more vectors


force that acts between materials that touch as they move past each other


the property of a body to resist changes to its state of motion

Newton's first law (law of intertia)

Newton's first law states that every object continues in a state of rest, or of uniform speed in a straight line, unless acted on by a nonzero net force.


the fundamental unit of mass


measure of the amount of material (matter) in an object and depends only on the number of and kind of atoms that compose it


measure of the gravitational force acting on the object. Depends on object's location


SI unit of force (1kg=10N)


in respect to (An object is moving if its position, relative to a fixed point, is changing


how fast an object is moving

instantaneous speed

the speed at any instant (tell speed of a car any instant by looking at speedometer)

average speed

the total distance covered divided by time


how fast and in what direction an object moves


rate at which velocity is changing. Change of velocity/time interval

Free fall

when an object is only affect by the force of gravity

Elapsed time

time that has elapsed, of passed, since the beginning of any motion


two vectors at right angles that add up to a given vector


process of determining the components of a vector


any object that moves through the air or space, acted on only by gravity (and air resistance, if any).


the path of a projectile


two values change in opposite directions. Mathematically we see that as the denominator increases, the whole quantity decreases by the same factor.

Newton's Second Law

the acceleration produced by a net force on an object is directly proportional to the marnitue of the net force, is in the same direction as the net force, and is inversely proportional to the mass of the object. Acceleration = net force/mass (a=F/m)


liquids and gases

air resistance

friction acting on something moviing through the air, a common form of fluid friction.

Free body diagram

diagram showing all the forces acting on an object


the amount of force per unit of area. Pressure = force/area of application (P=F/A)

Pascals (Pa.)

pressure is measured in newtons per square meter. Equal to one newton per square newton.

Terminal speed

speed at which the acceleration of a falling object is zero because friction balances the weight

Terminal velocity

terminal speed combined with non changing direction of motion


a mutual action between one thing and another

Newton's third law

whenever one object exerts a force on a second object, the second object exerts an equal and opposite force on the first object. One force is called the action force and the other the reaction force

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