Physics

# Section Summary

PhysicsSection Summary

### 1.1Physics: Definitions and Applications

• Physics is the most fundamental of the sciences, concerning itself with energy, matter, space and time, and their interactions.
• Modern physics involves the theory of relativity, which describes how time, space and gravity are not constant in our universe can be different for different observers, and quantum mechanics, which describes the behavior of subatomic particles.
• Physics is the basis for all other sciences, such as chemistry, biology and geology, because physics describes the fundamental way in which the universe functions.

### 1.2The Scientific Methods

• Science seeks to discover and describe the underlying order and simplicity in nature.
• The processes of science include observation, hypothesis, experiment, and conclusion.
• Theories are scientific explanations that are supported by a large body experimental results.
• Scientific laws are concise descriptions of the universe that are universally true.

### 1.3The Language of Physics: Physical Quantities and Units

• Physical quantities are a characteristic or property of an object that can be measured or calculated from other measurements.
• The four fundamental units we will use in this textbook 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.
• 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.
• Accuracy of a measured value refers to how close a measurement is to the correct value. The uncertainty in a measurement is an estimate of the amount by which the measurement result may differ from this value.
• Precision of measured values refers to how close the agreement is between repeated measurements.
• Significant figures express the precision of a measuring tool.
• When multiplying or dividing measured values, the final answer can contain only as many significant figures as the least precise value.
• When adding or subtracting measured values, the final answer cannot contain more decimal places than the least precise value.