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Physics

# Key Terms

PhysicsKey Terms

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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
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
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 quantity
physical quantity defined using algebraic combinations of base quantities
derived units
units that are derived by combining the fundamental physical units
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 $y=k/x y=k/x$ 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 $y=a x 2 +bx+c y=a x 2 +bx+c$, 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.
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, $y=mx+b y=mx+b$
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
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