12479542.ppt
- 1. C H A P T E R 1 Introduction and The Nature of Physics 1.1 Physics: An Introduction 1.2 Physical Quantities and Units 1.3 Accuracy, Precision, and Significant Figures 1.4 Approximation
- 2. The Nature of Physics • The word physics comes from Greek, meaning nature. The study of nature came to be called “natural philosophy.” • Physics is the study of the fundamental laws of nature. • Physics deals with the behavior and structure of matter. • Physics is very fundamental and the most basic of the sciences. • Physics can predict how nature will behave in one situation on the basis of experimental data obtained in another situation.
- 3. Sub-Fields of Physics Introductory physics is divided into the following sub-fields: • Mechanics (Chapters 1-12) • Thermal physics (Chapters 13-15) • Wave motion and sound (Chapters 16-17) • Electricity and magnetism (Chapters 18-24) • Light and optics (Chapters 25-27) • Modern physics (Chapters 28-34)
- 4. Relativistic Quantum Mechanics Modern physics: relativity (very fast) and quantum mechanics (very small). Relativity must be used whenever an object is traveling at greater than about 1% of the speed of light or experiences a strong gravitational field such as that near the Sun. Quantum mechanics must be used for objects smaller than can be seen with a microscope. The combination of these two theories is relativistic quantum mechanics, and it describes the behavior of small objects traveling at high speeds or experiencing a strong gravitational field. Relativistic quantum mechanics is the best universally applicable theory we have.
- 5. Historical Development • Models, Theories, and Laws • The Scientific Method • The Evolution of Natural Philosophy into Modern Physics Aristotle (384–322 B.C.) Galileo Galilei (1564–1642) Isaac Newton (1642–1727) Niels Bohr (1885–1962)
- 6. Units of Measurement System SI CGS BE
- 7. Units of Measurement System SI CGS BE Length meter (m) centimeter (cm) foot (ft)
- 8. Units of Measurement System SI CGS BE Length meter (m) centimeter (cm) foot (ft) Mass kilogram (kg) gram (g) slug (sl)
- 9. Units of Measurement System SI CGS BE/USC Length meter (m) centimeter (cm) foot (ft) Mass kilogram (kg) gram (g) slug (sl) Time second (s) second (s) second (s) SI stands for the French phrase "Le Systeme International d'Unitus." CGS - centimeter (cm), gram (g), and second. BE/USC - British Engineering/US Customary. http://physics.nist.gov/cuu/Units/
- 10. Physical Quantity Unit Name Symbol Time second s Length meter m Mass kilogram kg Electric current ampere A Temperature kelvin K Amount of substance mole mol Luminous intensity candela cd SI Base Quantities and Units: There are 7 of them Units named after people are capitalized.
- 11. Some SI Derived Quantities and Units • Area - m2 • Volume - m3 • Density - kg/m3
- 12. The meter In 1792 the meter was defined to be one ten- millionth of the distance from the north pole to the equator of the Earth. A C B Earth Equator 7 1 m 10 AB For practical reasons the meter was later (1799) defined as the distance between two fine lines on a standard meter bar made of platinum-iridium. In 1960, a new standard for the meter, based on the wavelength of light, was adopted. Specifically, the standard for the meter was redefined to be 1 650 763.73 wavelengths of a particular orange-red light emitted by atoms of krypton-86 in a gas discharge tube. Today (since 1983) the meter is defined as the length traveled by light in vacuum during the time interval of 1/299792458 of a second. This is because the measurement of the speed of light had become extremely precise. Speed of light: C=299792458 m/s
- 13. The second Initially the second was defined using Earth’s rotation: 1 1 second 24 60 60 of the time it takes the Earth to complete a full rotation about its axis. The problem with this definition is that the length of the day is not constant as is shown in the figure. Since 1967 the second is defined as the time taken by 9192631770 light oscillations of a particular wavelength emitted by a cesium-133 atom. This definition is so precise that it would take two cesium clocks 6000 years before their readings would differ by more than 1 second.
- 14. Standard Kilogram Today The SI standard of mass is a platinum- iridium cylinder shown in the figure. The cylinder is kept at the International Bureau of Weights and Measures in Sevres, Paris and assigned a mass of 1 kilogram. Accurate copies have been sent to other countries. A Second Mass Standard: The masses of atoms can be compared with one another more precisely than they can be compared with the standard kilogram. For this reason, we have a second mass standard. It is the carbon-12 atom, which, by international agreement, has been assigned a mass of 12 atomic mass units (u).
- 16. Accuracy and Precision Accuracy is how close a measurement is to the correct value for that measurement. The precision of a measurement system is refers to how close the agreement is between repeated measurements. Low precision and high accuracy High precision and low accuracy
- 17. Significant Figures Expressing the significant figures: In Calculations: For multiplication and division: The result should have the same number of significant figures as the quantity having the least significant figures entering into the calculation. For addition and subtraction: The answer can contain no more decimal places than the least precise measurement.
- 18. Approximation