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Физика для колледжа

College Physics 2e

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Бесплатный учебник, по которому учатся миллионы студентов-первокурсников. Первая глава о том, как физика измеряет мир: единицы, степени десяти, перевод единиц, точность, значащие цифры и быстрые оценки.

Это пробная часть: 1 из 34 (главы).

Из лекций

A phone with a blue dot on a road, two satellites above it with distance lines to the phone, and the relation distance equals speed times time beside them.
One law for chips and batteries

Physics behind the map

Physics describes how electricity moves through its circuits, and engineers use that knowledge to choose the materials and lay out the circuits when they build one.

A law box, an arrow to a prediction, then a test; a check mark keeps the law, a cross sends an arrow back to change it.
Laws, theories and a car that won't start

Valid until contradicted

Laws and theories are not just tidy summaries of old facts. Often, once one is in place, it points scientists to something nobody had found yet, sometimes even an object or event that had never been seen.

A small metal cylinder under a glass bell, with specks of dust on it, replaced by the formula involving Planck's constant h.
A meter of light, a kilogram of constants

The kilogram leaves its cylinder

The kilogram followed a similar road, only later. For more than a century it was a small cylinder of platinum and iridium, kept with the old meter bar at the international bureau of weights and measures near Paris.

The calculation 80 m times 1 km over 1000 m equals 0.080 km, with both m units struck through.
From a proton to the edge of the universe

A conversion factor cancels units

With so many sizes and so many units in use, we keep needing to change from one unit to another. A European recipe asks for milk in liters and your measuring jug shows cups; walking directions give a distance in feet and you want to know how many miles that is.

A thermometer reading 37 degrees with a band from 34 to 40, cold and fever marked at its ends.
Give or take

A thermometer three degrees off

Why does this matter so much? The book's answer is a sick child. You suspect a fever and reach for a thermometer, but imagine that it could be off by three degrees Celsius either way.

A stick figure 2 m tall beside a building drawn as stacked storeys, each two people high, totalling about 156 m.
Honest digits and bold guesses

A building in people

Now the book turns the whole question around. Very often, scientists and engineers do not need many digits at all. They need a quick, sensible estimate, which the book cheerfully calls a guesstimate.

Как это сделано

Примеры для: a curious adult with school maths; add one modern instance per idea, such as a phone, a GPS, a kitchen scale, a car speedometer or a medicine dose

Источник

Лекции пересказывают с английского оригинала книгу OpenStax College Physics 2e, CC BY 4.0 edition (GitHub openstax/osbooks-college-physics-bundle at f98d7a792138), автор — Пол Питер Уроне, Роджер Хинрикс (OpenStax); книга вышла под открытой лицензией, которая разрешает пересказ и перевод. Пересказ, рисунки и голос сделаны ИИ и сверены с книгой второй моделью. Как используется ИИ.

Лекции — переработка оригинала и распространяются под той же лицензией: их можно свободно распространять и перерабатывать с указанием автора и ссылкой на эту страницу: CC BY 4.0

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