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Key Terms

# Key Terms

binding energy
the energy equivalent of the difference between the mass of a nucleus and the masses of its nucleons
ether
scientists once believed there was a medium that carried light waves; eventually, experiments proved that ether does not exist
frame of reference
the point or collection of points arbitrarily chosen, which motion is measured in relation to
general relativity
the theory proposed to explain gravity and acceleration
inertial reference frame
a frame of reference where all objects follow Newton’s first law of motion
length contraction
the shortening of an object as seen by an observer who is moving relative to the frame of reference of the object
mass defect
the difference between the mass of a nucleus and the masses of its nucleons
postulate
a statement that is assumed to be true for the purposes of reasoning in a scientific or mathematic argument
proper length
the length of an object within its own frame of reference, as opposed to the length observed by an observer moving relative to that frame of reference
relativistic
having to do with modern relativity, such as the effects that become significant only when an object is moving close enough to the speed of light for$γ γ$to be significantly greater than 1
relativistic energy
the total energy of a moving object or particle$E=γmc2, E=γmc2,$ which includes both its rest energy mc2 and its kinetic energy
relativistic factor
$γ=11−u2c2 γ=11−u2c2$, where u is the velocity of a moving object and c is the speed of light
relativistic momentum
p = γmu, where$γ γ$is the relativistic factor, m is rest mass of an object, and u is the velocity relative to an observer
relativity
the explanation of how objects move relative to one another
rest mass
the mass of an object that is motionless with respect to its frame of reference
simultaneity
the property of events that occur at the same time
special relativity
the theory proposed to explain the consequences of requiring the speed of light and the laws of physics to be the same in all inertial frames
time dilation
the contraction of time as seen by an observer in a frame of reference that is moving relative to the observer