Glossary

accuracy
the degree to which a measured value agrees with 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 of measurement 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, 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 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
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; it is 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
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 that the scientist will research; next, the scientist typically performs some research about the topic and then devises a hypothesis; then, the scientist will test the hypothesis by performing an experiment; finally, the scientist analyzes the results of the experiment and draws 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
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