Sections

Key Terms
# Key Terms

- accuracy
- how close a measurement is to the correct value for that measurement

- ampere
- the SI unit for electrical current

- atom
- smallest and most basic units of matter

- classical physics
- physics, as it developed from the Renaissance to the end of the nineteenth century

- constant
- a quantity that does not change

- conversion factor
- a ratio expressing how many of one unit are equal to another unit

- dependent variable
- the vertical, or
*y*-axis, variable, which changes with (or is dependent on) the value of the independent variable

- derived units
- units that are derived by combining the fundamental physical units

- English units
- (also known as the customary or imperial system) system of measurement used in the United States; includes units of measurement such as feet, gallons, degrees Fahrenheit, and pounds

- experiment
- process involved with testing a hypothesis

- exponential relationship
- relation between variables in which a constant change in the independent variable is accompanied by change in the dependent variable that is proportional to the value it already had

- fundamental physical units
- the seven fundamental physical units in the SI system of units are length, mass, time, electric current, temperature, amount of a substance, and luminous intensity

- hypothesis
- testable statement that describes how something in the natural world works

- independent variable
- the horizontal, or
*x*-axis, variable, which is not influence by the second variable on the graph, the dependent variable

- inverse proportionality
- a relation between two variables expressible by an equation of the form $y=k/x$ where
*k*stays constant when*x*and*y*change; the special form of inverse relationship that satisfies this equation

- inverse relationship
- any relation between variables where one variable decreases as the other variable increases

- kilogram
- the SI unit for mass, abbreviated (kg)

- linear relationships
- relation between variables that produce a straight line when graphed

- log-log plot
- a plot that uses a logarithmic scale in both axes

- logarithmic scale
- a graphing scale in which each tick on an axis is the previous tick multiplied by some value

- meter
- the SI unit for length, abbreviated (m)

- method of adding percents
- calculating the percent uncertainty of a quantity in multiplication or division by adding the percent uncertainties in the quantities being added or divided

- model
- system that is analogous to the real system of interest in essential ways but more easily analyzed

- modern physics
- physics as developed from the twentieth century to the present, involving the theories of relativity and quantum mechanics

- observation
- step where a scientist observes a pattern or trend within the natural world

- order of magnitude
- the size of a quantity in terms of its power of 10 when expressed in scientific notation

- physics
- science aimed at describing the fundamental aspects of our universe—energy, matter, space, motion, and time

- precision
- how well repeated measurements generate the same or closely similar results

- principle
- description of nature that is true in many, but not all situations

- quadratic relationship
- relation between variables that can be expressed in the form $y=a{x}^{2}+bx+c$, which produces a curved line when graphed

- quantum mechanics
- major theory of modern physics which describes the properties and nature of atoms and their subatomic particles

- science
- the study or knowledge of how the physical world operates, based on objective evidence determined through observation and experimentation

- scientific law
- pattern in nature that is true in all circumstances studied thus far

- scientific methods
- techniques and processes used in the constructing and testing of scientific hypotheses, laws, and theories, and in deciding issues on the basis of experiment and observation

- scientific notation
- way of writing numbers that are too large or small to be conveniently written in simple decimal form; the measurement is multiplied by a power of 10, which indicates the number of placeholder zeros in the measurement

- second
- the SI unit for time, abbreviated (s)

- semi-log plot
- A plot that uses a logarithmic scale on one axis of the graph and a linear scale on the other axis.

- SI Units
- International System of Units (SI); the international system of units that scientists in most countries have agreed to use; includes units such as meters, liters, and grams; also known as the metric system

- significant figures
- when writing a number, the digits, or number of digits, that express the precision of a measuring tool used to measure the number

- slope
- the ratio of the change of a graph on the
*y*axis to the change along the*x-*axis, the value of*m*in the equation of a line, $y=mx+b$

- theory
- explanation of patterns in nature that is supported by much scientific evidence and verified multiple times by various groups of researchers

- theory of relativity
- theory constructed by Albert Einstein which describes how space, time and energy are different for different observers in relative motion

- uncertainty
- a quantitative measure of how much measured values deviate from a standard or expected value

- universal
- applies throughout the known universe

*y*-intercept- the point where a plot line intersects the
*y*-axis