Ch.1 Physics & Measurement Flashcards
The main objectives of physics are to identify a limited number of fundamental lawas that govern natural phenomena and use them to develop theories that can predict the results of future experiments.
When there is a discrepency between the prediction of a theory and experimental results, new or modified ________ must be formulated to remove the discrepancy.
theories
For example (new/modified theories), the laws of motion discovered by Isaac Newton (1642-1727) accurately describe the motion of objects moving at ___________ but do not apply to objects moving at speeds comparable to the speed of light. In contrast, the special _____________ developed later by Albert Einstein (1879-1955) gives the same results as Newton’s laws at low speeds but also correctly describes the motion of objects as speeds approaching the ______________.
normal speeds
theory of relativity,
speed of light
Classical physics includes the principles of classical mechanics, thermodynamics, optics and electromagnetism developed before _____. Important contributions to classical physics were provided by Newton, who was also one of the originators of ________ as a mathematical tool.
1900,
Calculus
Major developments in mechanics continued in the 18th century, but the fields of thermodynamics and electromagnetism were not developed until the latter part of the 19thcentury, principally b/c before that time, the apparatus for controlled experiments in these dissciplines was either ___________ or ___________.
too crude,
unavailable
A major revolution in pyhysics, usually referred to as ___________, began near the end of the 19th century.
modern physics
Modern physics developed mainly because many physical phenomena could not be explained by classical physics. The two most important developments in this modern era, were the _________________ and ____________.
theories of relativity,
quantum mechanics
Einstein’s special theory of relativity not only correctly describes the motion of objects moving at speeds comparable to the speed of light, it also completely modifies the traditional concepts of _______, _______, and _________.
space,
time,
energy
The theory of relativity also shows that the _______________ is the upper limit of the speed of an object and that _______ and ________ are related.
speed of light,
mass,
energy
_____________ was formulated by a number of distinguised scientists to provide descriptions of physical phenomena at the atomic level.
Quantum mechanics
To describe natural phenomena, we must make ____________ of various aspects of nature. Each measurement is associated w/ a physical quantity, such as the length of an object.
measurements
The laws of physics are expressed as ______________ among physical quantities.
mathematical relationships
If we are to report the results of a measurement to someone who wishes to reproduce this measurement, a ________ must be defined. It would be meaningless if a visitor from another planet were to talk to us about a length of 8 “glitches” if we do not know the meaning of the unit glitch.
standard
In 1960, an international committe established a set of standards for the fundamental quantities of science. It is called the __________________.
SI (Systeme International)
Some standards for SI fundamental units established by the committee are those for length (_____), mass (_____), temperature (_____), time (_____), and amount of a substance (_____).
meter, kg, K (Kelvin), seconds, moles
We can identify _______ as the distance b/w two points in space.
length
In 1799, the standard unit of length in France became the _______.
This was defined as one ten-millionth of the length of the distance from the ________ to the _________ along one particular longitudinal line that passes through Paris. Notice that this value is Earth-based and connot be used throughout the Universe.
meter.
equator, North Pole
As recently as 1960, the meter was defined as the distance between two lines on a specific _____________ stored under controlled conditions in France.
Current requirements of science and technology, however, necessitate more accuracy than that with which the separation b/w the lines on the bar can be determined.
platinum-iridium bar
In 1960s and 1970s, the meter was defined as 1650763.73 __________ of orange-red light emitted from a krypton-86 lamp.
In Oct. 1983, the meter was redfined as the dist. traveleled by __________ during a time of 1/299 792 458 seconds. This establishes that the speed of light in vacuum is precisely ____________.
wavelengths
light in vacuum,
299 792 458 m/s
In 1887, the SI unit of mass (_____) is defined as the mass of a specific _______________ kept at the International Bureau of Weights and Measures at Sevres, France. This standard has not been changed b/c ______________ is an unusually stable alloy. A duplicate of this alloy is kept at the National Institute of Standards and Technology (NIST) in _______________.
kg,
platinum-iridium alloy cylinder,
platinum-iridium alloy cylinder,
Gaithersburg, Maryland
Before 1967, the standard of time was defined in terms of the mean ________ (A _______ is the time interval b/w successive appearances of the Sun at the highest pt. it reaches in the sky each day).
solar day,
solar day
The SI unit of time (_____) was defined as (1/60)(1/60)(1/24) of a mean solar day. This defn is based on the rotation of one planet, the Earth. Therefore, this motion doesn’t provide a time standard that is __________.
seconds,
universal.
In 1967, the second was redefined to take advantage of the high precision attainable in a device known as an __________. This device measures vibrations of ___________. One second is now defined as 9 192 631 770 times the period of vibration of radiation from the cesium-133 atom. (Period is defined as ______________________________).
atomic clock,
cesium atoms,
the time interval necessary to complete vibration.
The variables length, time and mass are examples of __________________. Most other variables are __________________, those that can be expressed as a mathematical combination of fundamental quantities. Common examples are area and speed.
fundamental quantities,
derived quantities
Another example of derived quantity is density. The desity p (Greek letter rho) of any substance is defined as its mass per unit volume. Eq: __________.
p = M/V or D = M/V
In terms of fundamental quantities, density is a ratio of mass to a product of three _______. Aluminum, for example, has a density of 2.70*10^3 kg/m^3. An extreme difference in density can be imagined by thinking about holding a 10-cm^3 of Styrofoam in one hand and a 10-cm^3 of lead in the other.
lengths
If scientists cannot interact with a phenomenon directly, the would imagine a ______ for a physical system that is related to that phenomenon. For example, an atom is too small to interact with directly, so we make a model of an atom to make predictions about it.
model,
In Greek, atomos means “___________”. From this Greek terms, comes our English word ______.
not slicable,
atom
Protons, neutrons, and a host of other exotic particles are now known to be composed of six different varieties of particles called ________, which have been given the names of up, down, _______, _______, bottom, and top.
quarks,
strange, charmed
The up, charmed and top quarks have electric charges of ____ that of the proton, whereas the down, strange, and bottom quarks have the charges of ____ that of the proton.
+2/3,
-1/3
The proton consists of two “______” quarks and one “______” quark, labeled u and d. This structure predicts the correct charge for the proton (Fig. 1.2 in book, pg.6).
up,
down.
The neuron consists of two “______” quarks and one “______” quarks. Together, the proton and neutron net a charge of ___.
down,
up,
0
Table 1.5 (pg.7) Dimensions and Units of Four Derived Quantities
Qty. Area Vol.(V) Speed(v) Accel. (a)
Power L^2 L^3 L/T L/T^2
SI Unit m^2 m^3 m/s m/s^2
US Unit ft^2 ft^3 ft/s ft/s^2
