Chapter 0: Introduction — Review and Exercises
Chapter contents: Chapter 0: Introduction
Glossary
classical physics
physics that was developed from the Renaissance to the end of the 19th century
conversion factor
a ratio expressing how many of one unit are equal to another unit
derived units
units that can be calculated using algebraic combinations of the fundamental units
English units
system of measurement used in the United States; includes units of measurement such as feet, gallons, and pounds
fundamental units
base units chosen for a system of quantities; other units are formed from combinations of these units
kilogram
the SI unit for mass, abbreviated (kg)
law
a description, using concise language or a mathematical formula, a generalized pattern in nature that is supported by scientific evidence and repeated experiments
meter (unit of length)
the SI unit for length, abbreviated (m)
metric system
a system of measurement using decimal multiples and submultiples of units; SI is its modern international form
model
representation of something that is often too difficult (or impossible) to display directly
modern physics
the study of relativity, quantum mechanics, or both
order of magnitude
refers to the size of a quantity as it relates to a power of 10
physical quantity
a characteristic or property of an object that can be measured or calculated from other measurements
physics
the science concerned with describing the interactions of energy, matter, space, and time; it is especially interested in what fundamental mechanisms underlie every phenomenon
scientific method
a method that typically begins with an observation and question that the scientist will research; next, the scientist typically performs some research about the topic and then devises a hypothesis; then, the scientist will test the hypothesis by performing an experiment; finally, the scientist analyzes the results of the experiment and draws a conclusion
second
the SI unit for time, abbreviated (s)
SI units
units of the International System of Units, including base units such as the metre, kilogram, and second, and derived units such as the newton and joule
theory
an explanation for patterns in nature that is supported by scientific evidence and verified multiple times by various groups of researchers
units
a standard used for expressing and comparing measurements
Section Summary
0.2: Physics: An Introduction
- Science seeks to discover and describe the underlying order and simplicity in nature.
- Physics is the most basic of the sciences, concerning itself with energy, matter, space and time, and their interactions.
- Scientific laws and theories express the general truths of nature and the body of knowledge they encompass. These laws of nature are rules that all natural processes appear to follow.
0.3: Physical Quantities and Units
- Physical quantities are a characteristic or property of an object that can be measured or calculated from other measurements.
- Units are standards for expressing and comparing the measurement of physical quantities. SI uses seven base units: the meter, kilogram, second, ampere, kelvin, mole, and candela. Units for other quantities are derived from combinations of base units.
- Four base units used frequently in this text are the meter (for length), the kilogram (for mass), the second (for time), and the ampere (for electric current). These units are part of the metric system, which uses powers of 10 to relate quantities over the vast ranges encountered in nature.
- These four base units are abbreviated as follows: meter, m; kilogram, kg; second, s; and ampere, A. The metric system also uses a standard set of prefixes to denote each order of magnitude greater than or lesser than the fundamental unit itself.
- Unit conversions involve changing a value expressed in one type of unit to another type of unit. This is done by using conversion factors, which are ratios relating equal quantities of different units.
Questions and Exercises
0.2: Physics: An Introduction
Exercise 1
Give an example of physics used in each of two fields, such as biology, medicine, architecture, or geology. Identify the physical phenomenon involved in each example.
Exercise 2
Models are particularly useful in relativity and quantum mechanics, where conditions are outside those normally encountered by humans. What is a model?
Exercise 3
How does a model differ from a theory?
Exercise 4
What determines the validity of a theory?
Exercise 5
If two different theories describe experimental observations equally well, can one be said to be more valid than the other (assuming both use accepted rules of logic)?
Exercise 6
Certain criteria must be satisfied if a measurement or observation is to be believed. Will the criteria necessarily be as strict for an expected result as for an unexpected result?
Exercise 7
Can the validity of a model be limited, or must it be universally valid? How does this compare to the required validity of a theory or a law?
Exercise 8
Classical physics is a good approximation to modern physics under certain circumstances. What are they?
Exercise 9
Can classical physics be used to accurately describe a satellite moving at a speed of 7500 m/s? Explain why or why not.
Exercise 10
When is it necessary to use relativistic quantum mechanics?
0.3: Physical Quantities and Units
Exercise 11
How many fundamental units are there? What is the key difference between derived and fundamental units?
Exercise 12
Classify the following units as SI or U.S. customary: meter, second, kilogram, centimeter, square meter, meter per second, foot, and pound. Among the SI units listed, identify the base units, the unit formed by adding a prefix to the meter, and the units formed by combining base units.
Exercise 13
Identify some advantages of metric, or SI units.
Exercise 14
Identify some advantages and disadvantages of English, or imperial units.
Exercise 15
Explain why multiplying a distance expressed in kilometers by changes its numerical value without changing the distance. What happens to the units?
Exercise 16
A road has a posted speed limit of 65 miles per hour. Express this speed in (a) kilometers per hour and (b) meters per second. Use 1 mile = 1.609 kilometers and 1 hour = 3600 seconds. Round your answers to the nearest whole number.
Exercise 17
A tectonic plate moves at an average speed of 4 centimeters per year. If it maintains this speed, how far does it travel in one million years? Express your answer in kilometers. Explain why a small annual motion can matter over long periods of time.
Source sections: Physics: An Introduction, Physical Quantities and Units. Credits and licenses appear with each source section.