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 $y = a x^{2} + b x + c$ , 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, $y = m x + b$

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