Physics Ch 1 Flashcards
Law of Conservation of Energy
energy can change form but it never lost
Physics
Greek for “nature”; concerned with describing the interactions of energy, matters, space, and time; essentially interested in what fundamental mechanisms underlie each phenomenon; used to be bundled with astronomy, biology, chemistry, math, and medicine and called natural philosophy
Realm of Physics
concern for describing the basic phenomena in nature
Cornerstone of discovering natural laws
observation
Model
representation of something that is often too difficult (or impossible) to display directly; justified with experimental proof
Theory
explanation for patterns in nature that is supported by scientific evidence and verified multiple times by various groups of researchers; may or may not use models; complex, dynamic, does not try to be concise; end result of the process of the scientific method; large-scale, broadly applicable generalization
Law
uses concise language to describe a generalized pattern in nature that is supported by scientific evidence and repeated experiments; can often be expressed as a mathematical equation; postulate that forms the foundation of the scientific method
Force
mass times acceleration
Principle
less broadly applicable statements than laws or theories; distinction between laws and these often not carefully made
Scientific Method
as scientists inquire and gather information about the world they follow this process; starts with observation/question –> research –> hypothesis –> experiment –> analyze results –> conclude
Classical Physics
physics as it developed from the Renaissance to the end of the 19th century; not an exact description of the universe, but excellent approximation under following conditions: matter moving at less than 1% speed of light, objects large enough to be seen with microscope, only weak gravitational fields involved (like field generated by Earth)
Modern Physics
Physics from the beginning of the 20th century; consists of 2 revolutionary theories, relativity and quantum mechanics (deal with the very fast and the very small)
Aristotle
384-322BC; Greek philosopher; wrote on a broad range of topics including physics, animals, the soul, politics, and poetry
Galileo Galilei
1564-1642; laid the foundation of modern experimentation and made contributions in math, physics, and astronomy
Niels Bohr
1885-1962; made fundamental contributions to the development of quantum mechanics, one part of modern physics
Relativity
must be used whenever an object is traveling at greater than about 1% the speed of light or experiences a strong gravitational field (such as that near the sun)
Quantum Mechanics
must be used for objects smaller than that can be seen with a microscope
Relativistic Quantum Mechanics
relativity + quantum mechanics; describes the behavior of small objects traveling at high speeds or experiencing a strong gravitational field; best universally applicable theory we have; mathematically complex (used only when necessary)
4 Fundamental Physical Quantities
length (meter), mass (kg), time (sec), and electric (ampere, A)
Physical Quantity
defined either by specifying how it is measured or by stating how it is calculated from other measurements
Units
measurements of physical quantities expressed in terms of these standardized values
SI Units
1 of 2 types of major systems of units in the world; AKA metric system; virtually every country in the world except the US uses; term derived from French for International System
English units
2nd of 2 types of major systems of units in the world; AKA customary or imperial system; historically used in nations once ruled by the British Empire, still widely used in the US
Fundamental Units
most physical quantities can be defined only in terms of the procedure used to measure them
Derived Units
all other physical quantities besides fundamental ones; can be expressed as algebraic combinations of length, mass, time, and current
Second (s)
for many years defined as 1/86,400 of a mean solar day; solar day is getting longer due to gradual slowing of Earth’s rotation, so now defined as 9,192,631,770 of Cesium atom vibrations (defined in 1967)
Meter (m)
1791 definition: 1/10,000,000 of distance from Equator to North Pole; 1889: distance between 2 engraved lines on a platinum-iridium bar (Paris); 1960: 1,650,763.73 wavelengths of orange light emitted by krypton atoms; 1983 (present definition): distance light travels in a vacuum in 1/299,792,458 of a second (which defines the speed of light as 299,792,458 meters/second)
Kilogram (kg)
mass of a platinum-iridium cylinder kept with old meter standard at the International Bureau of Weights and Measures (Paris); replica kept at US’ National Institute of Standards and Technology (NIST) in Gaithersburg, MD
Distance
Speed x time
Metric System
convenient for scientific and engineering calculations b/c the units are categorized by a factor of 10
Order of Magnitude
refers to the scale of a value expressed in the metric system; each power of 10 represents a different one of these (ex. 10^1, 10^2, 10^3…); if raised to the same power, said to be the same ______ __ __________; = ballpark estimate for the scale of a value
Metric Prefixes
exa (E): 10^18; peta (P): 10^15; tera (T): 10^12; giga (G): 10^9; mega (M): 10^6; kilo (k): 10^3; hecto (h): 10^2; deka (da): 10^1; deci (d): 10^-1; centi (c): 10^-2; milli (m): 10^-3; micro (mew): 10^-6; nano (n): 10^-9; pico (p): 10^-12; femto (f): 10^-15; atto (a): 10^-18
Conversion Factor
ratio expressing how many of one unit are equal to another unit
Average speed
distance/time
Firkin
nonstandard unit of volume once used to measure beer; ~34 liters
Accuracy
how close a measurement is to the correct value for that measurement
Precision
how close the agreement is between repeated measurements (repeated under the same conditions)
Uncertainty (delta A)
quantitative measure of how much your measured values deviate from a standard or expected value; accuracy and precision are related to this
Factors contributing to uncertainty
limitations of measuring device; skill of person making measurement; irregularities in object being measured; any other factors that affect the outcome (highly dependent on the situation)
Percent uncertainty (%unc)
delta A (=uncertainty) /A (=measurement) x 100%
Method of Adding Percents
if the measurements going into the calculation have small uncertainties (a few percent or less) then this method can be used for multiplication or division; states that 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
Significant figures
rule = last digit written down in a measurement is the 1st digit with some uncertainty; indicate the precision of a measuring tool that was used to measure a value
Sigfigs with multiplication/division
result should have the same # of sigfigs as the quantity having the LEAST sigfigs entering into the calculation
Sigfigs with addition/subtraction
answer can have no more DECIMAL PLACES that the least precise measurement
Approximations
guesstimates
