Physics!

What is science?

Science is the understanding of the behavior of nature based on observations, experiments, models, and testing.

Hypothesis

A statement that attempts to explain a set of facts and forms the basis for an experiment designed to test its truth.

Law

A description of a generalized pattern in nature that is supported by scientific evidence and repeated experiments.

Theory

An explanation for patterns in nature that is supported by scientific evidence and verified multiple times.

Scientific Notation

A method of writing a big number in a small form with exponents by eliminating many zeros.

Accuracy

The degree to which a measured value agrees with the correct value for that measurement.

Approximation

An estimated value based on prior experience and reasoning.

Classical Physics

Physics that was developed from the Renaissance to the end of the 19th century.

Conversion Factor

A ratio expressing how many of one unit are equal to another unit.

Derived Units

Units that can be calculated using algebraic combinations of the fundamental units.

English Units

A system of measurement used in the United States, including units like feet, gallons, and pounds.

Fundamental Units

Units that can only be expressed relative to the procedure used to measure them.

Kilogram (kg)

The SI unit for mass.

Meter (m)

The SI unit for length.

Percent Uncertainty

The ratio of the uncertainty of a measurement to the measured value, expressed as a percentage.

Vector

A quantity that has both magnitude and direction.

Scalar

A quantity that is described by magnitude, but not direction.

Acceleration

The rate of change in velocity; the change in velocity over time.

Deceleration

Acceleration in the direction opposite to velocity, resulting in a decrease in velocity.

Instantaneous Velocity

Velocity at a specific moment in time.

Displacement

The change in position of an object.

Free-Fall

The state of movement that results from gravitational force only.

Kinematics

The study of motion without considering its causes.

Projectile Motion

The motion of an object that is subject only to the acceleration of gravity.

Trajectory

The path of a projectile through the air.

Relative Velocity

The velocity of an object as observed from a particular reference frame.

Average Speed

Distance traveled divided by the time during which motion occurs.

Significant Figures

Express the precision of a measuring tool used to measure a value.

Science

The understanding of the behavior of nature based on observations, experiments, models, and testing; a methodology by which we try to understand nature and how it behaves.

Hypothesis

A statement that attempts to explain a set of facts that forms the basis for an experiment designed to test whether the statement is true or not.

Laws

Scientific knowledge that experiments have repeatedly verified and never proven wrong; their accuracy does not change when new theories are worked out, and they predict what will happen under specific conditions.

Theory

An explanation of an aspect of the natural world that accounts for a wider variety of events than a law does, can be repeatedly tested with the scientific method, withstands rigorous scrutiny, and embodies scientific knowledge.

Scientific Notation

A method of writing large or small numbers in a compact form with exponents by eliminating many zeros (e.g., $5{,}000{,}000{,}000$ is written as $5 \times 10^9$).

accuracy

The degree to which a measured value agrees with the correct value for that measurement.

approximation

An estimated value based on prior experience and reasoning.

classical physics

Physics that was developed from the Renaissance to the end of the 19th century.

conversion factor

A ratio expressing how many of one unit are equal to another unit.

derived units

Units that can be calculated using algebraic combinations of the fundamental units.

English units

System of measurement used in the United States; includes units such as feet, gallons, and pounds.

fundamental units

Units that can only be expressed relative to the procedure used to measure them.

kilogram

The SI unit for mass, abbreviated (kg).

law

A description, using concise language or a mathematical formula, of a generalized pattern in nature that is supported by scientific evidence and repeated experiments.

meter

The SI unit for length, abbreviated (m).

method of adding percents

The rule stating that the percent uncertainty in a quantity calculated by multiplication or division is the sum of the percent uncertainties in the items used to make the calculation.

metric system

A system in which values can be calculated in factors of $10$.

model (general)

A representation of something that is often too difficult (or impossible) to display directly.

modern physics

The study of relativity, quantum mechanics, or both.

order of magnitude

Refers to the size of a quantity as it relates to a power of $10$.

percent uncertainty

The ratio of the uncertainty of a measurement to the measured value, expressed as a percentage.

physical quantity

A characteristic or property of an object that can be measured or calculated from other measurements.

physics

The science concerned with describing the interactions of energy, matter, space, and time; especially interested in what fundamental mechanisms underlie every phenomenon.

precision

The degree to which repeated measurements agree with each other.

quantum mechanics

The study of objects smaller than can be seen with a microscope.

relativity (general)

The study of objects moving at speeds greater than about $1\%$ of the speed of light, or of objects being affected by a strong gravitational field.

scientific method

A method that typically begins with an observation and question, followed by research, formulation of a hypothesis, testing via experimentation, and analysis of results to draw a conclusion.

second

The SI unit for time, abbreviated (s).

SI units

The international system of units that scientists in most countries have agreed to use; includes units such as meters, liters, and grams.

significant figures

Express the precision of a measuring tool used to measure a value.

theory (definition)

An explanation for patterns in nature that is supported by scientific evidence and verified multiple times by various groups of researchers.

uncertainty

A quantitative measure of how much your measured values deviate from a standard or expected value.

units

A standard used for expressing and comparing measurements.

acceleration

The rate of change in velocity; the change in velocity over time.

acceleration due to gravity

Acceleration of an object as a result of gravity.

average acceleration

The change in velocity divided by the time over which it changes.

average speed

Distance traveled divided by time during which motion occurs.

average velocity

Displacement divided by time over which displacement occurs.

deceleration

Acceleration in the direction opposite to velocity; acceleration that results in a decrease in velocity.

dependent variable

The variable that is being measured; usually plotted along the $y$-axis.

displacement

The change in position of an object.

distance

The magnitude of displacement between two positions.

distance traveled

The total length of the path traveled between two positions.

elapsed time

The difference between the ending time and beginning time.

free-fall

The state of movement that results from gravitational force only.

independent variable

The variable that the dependent variable is measured with respect to; usually plotted along the $x$-axis.

instantaneous acceleration

Acceleration at a specific point in time.

instantaneous speed

Magnitude of the instantaneous velocity.

instantaneous velocity

Velocity at a specific instant, or the average velocity over an infinitesimal time interval.

kinematics (one-dimensional)

The study of motion without considering its causes.

model (kinematics)

A simplified description that contains only those elements necessary to describe the physics of a physical situation.

position

The location of an object at a particular time.

scalar

A quantity that is described by magnitude, but not direction.

slope

The difference in $y$-value (the rise) divided by the difference in $x$-value (the run) of two points on a straight line.

time

Change, or the interval over which change occurs.

vector

A quantity that is described by both magnitude and direction.

y-intercept

The $y$-value when $x = 0$, or when the graph crosses the $y$-axis.

air resistance

A frictional force that slows the motion of objects as they travel through the air; when solving basic physics problems, air resistance is assumed to be zero.

analytical method

The method of determining the magnitude and direction of a resultant vector using the Pythagorean theorem and trigonometric identities.

classical relativity

The study of relative velocities in situations where speeds are less than about $1\%$ of the speed of light—that is, less than $3000\,\text{km/s}$.

commutative

Refers to the interchangeability of order in a function; vector addition is commutative because the order in which vectors are added together does not affect the final sum.

component (of a 2-d vector)

A piece of a vector that points in either the vertical or the horizontal direction; every 2-D vector can be expressed as a sum of two vertical and horizontal vector components.

direction (of a vector)

The orientation of a vector in space.

head (of a vector)

The end point of a vector; the location of the tip of the vector's arrowhead; also referred to as the 'tip'.

head-to-tail method

A method of adding vectors in which the tail of each vector is placed at the head of the previous vector.

kinematics (two-dimensional)

The study of motion without regard to mass or force.

magnitude (of a vector)

The length or size of a vector; magnitude is a scalar quantity.

motion

Displacement of an object as a function of time.

projectile

An object that travels through the air and experiences only acceleration due to gravity.

projectile motion

The motion of an object that is subject only to the acceleration of gravity.

range

The maximum horizontal distance that a projectile travels.

relative velocity

The velocity of an object as observed from a particular reference frame.