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Key Terms

the degree to which a measured value agrees with an accepted reference value for that measurement
base quantity
physical quantity chosen by convention and practical considerations such that all other physical quantities can be expressed as algebraic combinations of them
base unit
standard for expressing the measurement of a base quantity within a particular system of units; defined by a particular procedure used to measure the corresponding base quantity
conversion factor
a ratio that expresses how many of one unit are equal to another unit
derived quantity
physical quantity defined using algebraic combinations of base quantities
derived units
units that can be calculated using algebraic combinations of the fundamental units
expression of the dependence of a physical quantity on the base quantities as a product of powers of symbols representing the base quantities; in general, the dimension of a quantity has the form LaMbTcIdΘeNfJgLaMbTcIdΘeNfJg for some powers a, b, c, d, e, f, and g.
dimensionally consistent
equation in which every term has the same dimensions and the arguments of any mathematical functions appearing in the equation are dimensionless
quantity with a dimension of L0M0T0I0Θ0N0J0=1;L0M0T0I0Θ0N0J0=1; also called quantity of dimension 1 or a pure number
the difference between the measured value and a given standard or expected value
English units
system of measurement used in the United States; includes units of measure such as feet, gallons, and pounds
using prior experience and sound physical reasoning to arrive at a rough idea of a quantity’s value; sometimes called an “order-of-magnitude approximation,” a “guesstimate,” a “back-of-the-envelope calculation”, or a “Fermi calculation”
SI unit for mass, abbreviated kg
description, using concise language or a mathematical formula, of a generalized pattern in nature supported by scientific evidence and repeated experiments
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
system in which values can be calculated in factors of 10
representation of something often too difficult (or impossible) to display directly
order of magnitude
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
characteristic or property of an object that can be measured or calculated from other measurements
science concerned with describing the interactions of energy, matter, space, and time; especially interested in what fundamental mechanisms underlie every phenomenon
the degree to which repeated measurements agree with each other
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
used to express the precision of a measuring tool used to measure a value
testable explanation for patterns in nature supported by scientific evidence and verified multiple times by various groups of researchers
a quantitative measure of how much measured values deviate from one another
standards used for expressing and comparing measurements
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