Physics Ch. 1
What is the order of magnitude of 297,395?
Log10(297,395) = 5.47. So the order of magnitude is 10^6.
meter
SI unit for length, abbreviated m
kilogram
SI unit for mass, abbreviated kg
What is the difference between SI and English units?
Si units - international system of units that scientists in most countries have agreed to use (i.e. m, L, kg). English units - system of units that is used widely only in the US (i.e. ft, gal, lbs)
What determines the validity of a theory?
Experimental tests produce results that confirm the theory.
If a quantity is dimensionless, what are its units?
The quantity has no units.
What is an order of magnitude?
The size of a quantity as it related to a power of 10.
Why are significant figures useful?
They are used to express the precision of a measuring tool used to measure a value
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
percent uncertainty
the ratio of the uncertainty of a measurement to the measured value, expressed as a percentage
order of magnitude
the size of a quantity as it relates to a power of 10
standard deviation of mean
the standard deviation of a set of measurements divided by the square root of the number of measurements in the set
How is the second defined in the metric system now?
time it takes for certain number (~9 Billion) vibrations of a Cesium atom
What are some examples of dimensions?
time, mass, mass squared (M^2), 1/length (1/L) ...
derived units
units that can be calculated using algebraic combinations of the fundamental units
significant figures
used to express the precision of a measuring tool used to measure a value
estimation
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"
standard deviation
a computed measure of how much scores vary around the mean score
uncertainty
a quantitative measure of how much measured values deviate from one another
What ratio (what divided by what?) is a conversion factor?
a ratio how many of one unit are equal to another unit: for example the first unit divided by the equal number of the other
conversion factor
a ratio that expresses how many of one unit are equal to another unit
dimensionless
quantity of dimension 1 or a pure number
model
representation of something often too difficult (or impossible) to display directly
physics
science concerned with describing the interactions of energy, matter, space, and time; especially interested in what fundamental mechanisms underlie every phenomenon
How should the conversion factor be chosen/mathematically arranged?
so the old unit cancels out
What are base units?
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
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
units
standards used for expressing and comparing measurements
metric system
system in which values can be calculated in factors of 10
English units
system of measurement used in the United States; includes units of measure such as feet, gallons, and pounds
theory
testable explanation for patterns in nature supported by scientific evidence and verified multiple times by various groups of researchers
second
the SI unit for time, abbreviated s
accuracy
the degree to which a measured value agrees with an accepted reference value for that measurement
precision
the degree to which repeated measurements agree with each other
discrepancy
the difference between the measured value and a given standard or expected value
experimental difference
the difference between two values being compared
SI units
the international system of units that scientists in most countries have agreed to use; includes units such as meters, liters, and grams
reliable standard unit must be...
-repeatable -accurate -transportable -long lasting
pico (p)
10^-12
femto (f)
10^-15
milli (m)
10^-3
micro (μ)
10^-6
nano (n)
10^-9
Tera (T)
10^12
kilo (k)
10^3
Mega (M)
10^6
Giga (G)
10^9
speed of light
3.00 x 10^8 m/s
What is the difference between accuracy and precision?
Accuracy - how close a measurement is to the accepted reference value for that measurement. Precision - how close the agreement is between repeated independent measurements
Physics is devoted to the understanding of what?
All natural phenomena which means all natural things that occur
How is a physical quantity defined?
Characteristic or property of an object that can be measured or calculated from other measurements.
What law ties together food calories, batteries, heat, light, and watch springs? What does it state?
Conservation of energy. Energy can change form but is never lost.
Describe the scope of physics. Describes the most basic understanding of phenomena.
Describes the interactions of matter, space, and time.
What is discrepancy or measurement error?
Difference between the measured value and an expected value.
Physics can be used to describe what aspects of smartphones?
Electricity flow through circuits and GPS.
Can the validity of a model be limited or must it be universally valid? How does this compare with the required validity of a theory or a law?
Models only need be accurate in describing certain aspects of a physical system. A theory or law must be valid in all situations.
steradian
Solid Angle of cone; ϴ= 1 steradian; 4pi steradians in a sphere
What is a unit?
Standards used for expressing and comparing measurements.
experimental error
The difference between the true value of a measurement and the measured value
Is the equation v=a*t dimensionally consistent?
Yes. [v] = [L]/[T] = [L]/[T^2] * [T] = [L]/[T].
What is a Fermi calculation?
an estimation
Is an order of magnitude designed to act more like an exact quantity or as a ballpark estimate?
ballpark estimate
How is the kg defined in the metric system now?
based on mass of a standard object at NIST
physical quantity
characteristic or property of an object that can be measured or calculated from other measurements
Is area a base or derived quantity?
derived
How do base units and quantities differ from derived quantities and units?
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.
law
description, using concise language or a mathematical formula, of a generalized pattern in nature supported by scientific evidence and repeated experiments
How is the meter defined in the metric system now?
distance light travels in 1/(light speed) of a second
dimensionally consistent
equation in which every term has the same dimensions and the arguments of any mathematical functions appearing in the equation are dimensionless
What does it mean for an equation to be dimensionally consistent?
every term has the same dimensions
dimension
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 L a MbT c I d Θ e N f J g for some powers a, b, c, d, e, f, and g
What force acts on the Whirlpool galaxy as well as Earth?
gravity
when S=R, ϴ = 1 radian or 1 rad...
here are 2pi radian in a circle of 360deg
What are the SI base units of length, mass, time, and thermodynamic temperature?
m kg, s, K
SI base units
meter, kilogram, second, kelvin, mole, ampere, candela
What are base quantities?
physical quantity chosen by convention and practical considerations such that all other physical quantities can be expressed as algebraic combinations of them
base quantity
physical quantity chosen by convention and practical considerations such that all other physical quantities can be expressed as algebraic combinations of them
derived quantity
physical quantity defined using algebraic combinations of base quantities
