# Physics Introduction, Measurements, and Estimating

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Douglas C. Giancoli – Physics for Scientists and Engineers with Modern Physics

Physics, like other sciences, is a creative endeavor. It is not simply a collection of facts. Important are created with the idea of explaining . To be accepted, theories are by comparing their predictions with the results of actual experiments. Note that, in general, a theory cannot be “proved” in an absolute sense.

Scientists often devise models of physical phenomena. A is a kind of picture or analogy that helps to describe the phenomena in terms of something we already know. A , often developed from a model, is usually deeper and more complex than a simple model.

A scientific is a concise statement, often expressed in the form of an equation, which quantitatively describes a wide range of phenomena.

play a crucial role in physics, but can never be perfectly precise. It is important to specify the of a measurement either by stating it directly using the ± notation, and/or by keeping only the correct number of .

Physical quantities are always specified relative to a particular standard or , and the unit used should always be stated. The commonly accepted set of units today is the Systéme International (SI), in which the standard units of length, mass, and time are the , , and .

When converting units, check all for correct cancellation of units.

Making rough, is a very useful technique in science as well as in everyday life.

The of a quantity refer to the combination of base quantities that comprise it. Velocity, for example, has dimensions of [length/time] or [L/T]. can be used to check a relationship for correct form.

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