Transcript File
What is Physics? What is Physics? • Physics is – the scientific study of the physical world: matter, energy, motion, and force. – The study of the fundamental laws of nature, which, simply put, are the laws that underlie all physical phenomena in the universe. • From a Greek term meaning "the science of nature." What is Physics? Continued • Physics is everywhere, in fact most people know more about it than they think they do – When you buy ice cream you know that you need to put it in the freezer. Why? Because it would melt otherwise. • Any problem that deals with temperature, size, motion, position, shape, or color involves physics. • We have remarkably found that these laws can be expressed in terms of mathematical equations. Areas within Physics Name Subjects Examples Mechanics Motion and its causes, interactions between objects Falling objects, friction, weight, spinning objects Thermodynamics Heat and Temperature Melting and freezing processes, engines, refrigerators Vibrations and Wave Phenomena Specific types of repetitive motions Springs, pendulums, sound Optics Light Mirrors, lenses, color, astronomy Electromagnetism Electricity, magnetism, and light Electrical charge, circuitry, permanent magnets, electromagnets Relativity Particles moving at any speed, including very high speeds Particle collisions, particle accelerators, nuclear energy Quantum mechanics Behavior of submicroscopic particles The atom and its parts This is Physics!! SI Units Quantity Name SI Abbreviation Length Meter m Mass Kilogram kg Time Second s Electric current Ampere A SI Prefixes • Prefixes are used to change the size of the base unit. Used instead of writing a lot of zeroes. Conversion Factors • Conversion factor – A ratio of equivalent measurements. – Useful in solving problems in which a given measurement must be expressed in some other unit of measurement. Dimensional Analysis • Dimensional analysis – A way to analyze and solve problems using the units of the measurements. Converting Between Units Multistep Problems Converting Complex Units Practice Problems • A minivan sells for 33,200 dollars. Express the price for a minivan in kilodollars and Megadollars? • A Typical E.coli bacterium is about 5 micrometers in length.Give the length in millimeters and kilometers. • How many seconds are in a leap year? • Convert the speed 5.30 m/s to km/h. Scientific Notation • Scientist often deal with very large or very small numbers. These numbers can be expressed in powers of 10 • Numbers take the form of – M X 10n • Where M = a number 1 – 10 • And n = the number of decimal places moved Conversions using Scientific Notation with large numbers • Ex 1 • Convert 1,500,000 to scientific notation. • First move the decimal place so that there is only one digit to its left • 1.5 • How many spaces did we move them? • 6 • So we write it as • 1.5 x 106 • • • • • • • • Conversions using Scientific Notation with small numbers Ex 1 Convert .000025 to scientific notation First move the decimal 2.5 How many places did we move it? 5 So we write it as: 2.5 x 10-5 (note: since the number was less than one it is written as a negative number) Sample Problems • Convert the following: – 5.65 x 106 – 4.90 x 10-4 – .000000045 – .0000067 Using Scientific Notation • Multiplication – The base numbers are multiplied and the exponents are added. • (4.0 x 103)(2.0 x 103) = • Division – The base numbers are divided and the exponents are subtracted. • (1.06 x 104)/(2.0 x 10-2) = • Addition or subtraction – Express all the exponents in the same power of 10. Perform the addition or subtraction, then if necessary convert to correct form of scientific notation. • 7.11 x 104 + 4.0 x 103 = Significant Figures (Sig Figs) • All Digits 1-9 are significant – – • Zeros between significant digits are significant – – • 100.0 4 sig figs 100 1 sig fig Zeros in the beginning of a number whose only function is to place the decimal points are not significant – – • 5,007 4 sig figs Trailing zeros are only significant if the number contains a decimal point – – – – • 129 3 sig figs 0.0025 2 sig figs Zeros following a decimal significant figure are significant – – – – 0.000470 3 sig figs 0.47000 5 sig figs Calculations using Sig Figs • When multiplying or dividing – Round to the least number of sig figs • When adding or subtracting – Round to the least amount of decimal places Sample Problems • • • • 6.201 cm + 7.4 cm + .68 cm + 12.0 cm 10.8 cm - 8.264 cm 139 cm x 2.3 cm 18.21 g 4.4 g Today’s Homework • Page 9 – 1, 2 • Page 20 – 1, 2, 3, • Pages 27 – 31 – 1,2,5,7,8,11,13,16,18,19,20,21,22