Chapter 1

• Physics is the most basic of the sciences, dealing with the behavior and structure of matter.
• The field of physics is usually divided into classical physics which includes motion, fluids, heat, sound, light, electricity, and magnetism; and modern physics which includes the topics of relativity, atomic structure, quantum theory, condensed matter, nuclear physics, elementary particles, and cosmology and astrophysics.
• Physics is the search for order in our observations of the world around us.
• Science, including physics, is a creative activity that resembles other creative activities of the human mind.
• Observation of events, which includes the design and carrying out of experiments, is a crucial aspect of science.
• Imagination is an integral part of observation and experiments in science.
• Scientists must make judgments about what is relevant in their observations and experiments.
• Aristotle (384 – 322 B.C.) and Galileo (1564 – 1642) interpreted motion along a horizontal surface differently.
• In the quest to understand the world around us, scientists seek to find relationships among physical quantities that can be measured.
• Physics relates to other fields in numerous ways, including aesthetics, psychology, and engineering.
• The purpose of a model is to give us an approximate mental or visual picture — something to hold on to — when we cannot see what actually is happening.
• A theory is broader, more detailed, and can give quantitatively testable predictions, often with great precision.
• The wave model of light is an example of a model, as experiments indicate that light behaves in many respects as water waves do.
• Scientific laws are different from political laws in that the latter are prescriptive, telling us how we ought to behave, while scientific laws are descriptive, describing how nature does behave.
• When scientists are trying to understand a particular set of phenomena, they often make use of a model, which is a kind of analogy or mental image of the phenomena in terms of something else we are already familiar with.
• Models often give us a deeper understanding, suggesting new experiments to perform and providing ideas about what other related phenomena might occur.
• Laws cannot be tested in the infinite variety of cases possible, so we cannot be sure that any law is absolutely true.
• Scientists normally do their research as if the accepted laws and theories were true, but they are obliged to keep an open mind in case new information should alter the validity of any given law or theory.
• Architects must be aware of the forces involved in a structure, as instability, even if only illusory, can be discomforting to those who must live or work in the structure.
• Studies on the forces in structures by Leonardo da Vinci (1452–1519) include a bridge over the River Tiber in Rome that is still standing after 2000 years and the 2007 collapse of a Mississippi River highway bridge built only 40 years before.
• A centiliter (cL) is 100 milliliters (mL), and a kilogram (kg) is 1000 grams (g).
• In the metric system, the larger and smaller units are defined in multiples of 10 from the standard unit, making calculation particularly easy.
• An 8.2-megapixel camera has a detector with 8,200,000 pixels (individual “picture elements”).
• The standard second is now defined in terms of the frequency of radiation emitted by cesium atoms when they pass between two particular states.
• Some typical lengths or distances are measured in meters, neutron or proton diameters, atom diameters, virus lengths, sheet of paper thicknesses, finger widths, football field lengths, heights of Mt. Everest, Earth diameters, Earth to Sun distances, Earth to nearest star distances, Earth to nearest galaxy distances, Earth to farthest galaxy visible distances, and time intervals such as the length of recorded history, human life span, and age of Earth and Universe.
• In common usage, 1 micron is referred to as a unit of length.
• When dealing with the laws and equations of physics, it is very important to use a consistent set of units.
• There are 60 seconds in one minute and 60 minutes in one hour.
• The unified atomic mass unit (u or amu) is often used in calculations involving atoms and molecules.
• The second was defined as a fraction of a mean solar day for many years.
• One second is defined as the time required for 9,192,631,770 oscillations of this radiation.
• The standard unit of mass is the kilogram (kg), defined as the mass of a particular platinum-iridium cylinder kept at the International Bureau of Weights and Measures near Paris, France.
• Jim stands beside a wide river and measures his stride to be about 0.8 m long, estimating the width of the river.
• A thousand cubic centimeters (10^3 cm^3) is approximately the volume of a 1-ton rock.
• The ratio of the volume of Earth compared to the volume of the Moon is approximately
• Walking around the Earth would take
• A watch manufacturer claims that its watches gain or lose no more than 8 seconds in a year, expressed as a percentage.
• The volume of something that weighs a ton is approximately the same as a rock, which has a mass per volume about 3 times that of water, or 1 kg per liter or 62 lb per cubic foot.
• The ratio of the surface area of Earth compared to the surface area of the Moon; the volume of Earth compared to the volume of the Moon; and the ratio of the mass of a human to the mass of a DNA molecule can be determined to the correct number of significant figures using the information inside the front cover of this book.
• A storm dumps 1.0 cm of rain on a city 6 km wide and 8 km long in a 2-h period, resulting in a total of 1.0 metric tons of water.