2. Chapter 1 The Science of Physics

3. Key Objectives Definition of Physics Areas within Physics Scientific Method Measurements and Units (SI) Accuracy and Precision Dimensional Analysis

4. Definition of Physics  Physics is the study of the physical world.  A science that deals with matter and energy and their interactions –Etymology: Latin physica, plural, natural science, from Greek physika, from neuter plural of physikos of nature, from physis growth, nature, from phyein to bring forth  Merriam-Webster Online Dictionary  Physics can be used to explain every object and phenomena around you.

5. Areas of Physics NameSubjects Mechanics Thermodynamics Vibrations and Waves Optics Electromagnetism Relativity Quantum Mechanics Motion and its causes Heat and Temperature Specific types of repetitive motion Light Electricity, Magnetism, & Light Particles moving at high speeds Behavior of submicroscopic particles

6. What is the Scientific Method? There is no single procedure that scientists follow in their work. But, there are certain steps common to all good scientific investigations. Those steps are called the scientific method. Observation Gather information that would lead to you to a question. Hypothesis Experiment Make an educated guess for an answer to your question Conclusion Perform an experiment and collect data to support your hypothesis. Make a final statement based on your findings to prove your hypothesis.

7. Units of Measurement There are many different systems of measurements in science. Here in the United States, we use the English system of units. milespoundsFahrenheit Other countries, such as Canada, use the Metric system of units. metergramCelsius Since the world cannot decide on what units to use, scientists have. We have come to a mutual agreement for a consistent system of units...

8. SI Units That mutual system is called the International System of units. We abbreviate it using SI, which is short for Systeme International. QuantityUnit Lengthmeter (m) Masskilogram (kg) Temperaturekelvin (K) Timesecond (s) Currentampere (A) Energyjoule (J) Forcenewton (N)

9. Standards of Length, Mass, and Time  We all know these are used to measure certain characteristics of the phenomena around us.  Before we knew of things such as the meter, or kilogram, or second, the quantities above had no standard way of being measured.  So how did we come to designate a certain distance, or time interval, or mass as being the standards for all measurements?  These 3 are a few examples of SI Base Units because they stand alone without deriving the units of measure from any other unit.

10. The Kilogram  The kilogram is defined as the mass of a specific platinum-iridium alloy cylinder kept as the International Bureau of Weights and Measures in Sèvres, France. –Platinum-Iridium alloy is a very stable metal with no tendency to rust or be chemically altered by its environment. –It is a disadvantage to maintain a measurement that way because it is only accessible to those in the institute.  So any other kilogram measurement is accepted to be so.

11. The Meter  The meter was originally defined in France as one ten-millionth of the distance from the Equator to the North Pole.  Until 1960, the meter was defined by the distance between two lines on a specific bar of platinum- iridium alloy. –Kept in the National Institute of Standards and Technology in Sèvres, France.  In 1983 the meter took on the current definition as the distance traveled by light in a vacuum during the time interval of 1/299,792,458 second. –v light = 299,792,458 m / s  v = fλ –λ = 1 / 299,792,458

12. The Second  Before 1960, the time standard was defined as the average length of a solar day in the year 1900. –A solar day is the time interval between successive appearances of the Sun at its highest point each day.  So that would be 1 / 86,400 of a day!  In 1967, we were able to take advantage of new technology in the atomic clock. –A clock that uses the frequency of the light emitted from the cesium-133 atom.  The second is now defined as 9,192,631,700 times the period of oscillation of radiation from the cesium atom.

13. Prefixes PrefixSymbolNumber pico- nano- micro- milli- centi- deci- kilo- mega- giga- p n μ m c d k M G.000000000001.000000001.000001.001.01.1 1000 1,000,000 1,000,000,000

14. Example 1.1 Give the numerical equivalent to the following measurements using the appropriate prefix. 1. 36 nanometers 1.36 nm 2. 463 kiloseconds 2.463 ks 3. 86 micrograms 3.86  g 4..1495 megajoules 4..1495 MJ

15. Example 1.2 Give the decimal equivalent to the following measurements in their base unit. 1. 7 dm 1.7 x 10 -1 m 0.7 m 2. 38 Gs 2.38 x 10 9 s 38,000,000,000 s 3. 423 pJ 3.423 x 10 -12 J.000 000 000 423 J

16. Accuracy v Precision Accuracy is how close a measured value is to the true value or accepted value. Precision is How close each measurement is to each other measurement. Our goal is to be both accurate and precise in our measurements.

17. Measuring Rules  Tools with open spaces between markings are accurate to one decimal place beyond the last marking. –So if the ruler has millimeter lines, then you read to 0.1 mm.  The last decimal that you added can be your best estimate. –So if it looks like it is half-way between millimeter lines, then your answer will be 0.5 mm  If the measuring equipment uses a digital readout, then we are as accurate as the manufacturer allows us to be. 3.8 mm

18. Significant Figures In order to be accurate and precise with our measurements, we must pay attention to significant figures while analyzing data on the calculator. The numbers 12 3 4 5 6 7 8 9 count as significant figures 0 is a significant figure under certain conditions It is used after a decimal point to show accuracy of measurement 4.23 00 It is trapped between other significant figures. 28042804 0 is not a significant if It is used as a place holder between significant figures and the decimal. 430430. 0 222

19. Example 1.3 Identify the number of significant figures found in the following measurements. 1. 203 mi 1.3 sig figs 2..0048 m 2.2 sig figs 3. 7700 kg 3.2 sig figs 4. 3.45 x 10 6 N 4.3 sig figs 5. 981.0 ± 0.1 s 5.4 sig figs Ignore the tolerance value of 0.1

20. Scientific Notation to the Rescue  What happens when the answer is rounded up or down to zero, and that zero is still significant?  ie: 4597 m (using 3 sig figs)  4600 m  In Physics: We will use scientific notation to show accuracy with significant figures.  ie: 4597 m (using 3 sig figs)  4.60 x 10 3 m

21. Addition & Subtraction To determine the number of significant figures you can keep when you are adding/subtracting measurements, you need to look at the least accurate measurement. That means the number showing the least amount of digits as you move right through the number. For instance: 46.4 Shows that we are accurate to the tenths place. 9.46 Shows we are accurate to the hundredths place. 270 Shows we are accurate to tens place! + When we add those together 325.86 We can only keep to the tens place. 330

22. Multiplication & Division Finding how many significant figures to keep with multiplication and division is much easier than with other operations. That is because you simply count how many significant figures are in each measurement, and keep the number of significant figures equivalent to the measurement with the least number. 46.40 Has 4 significant figures. 120.46 Has 5 significant figures 27.1 Has 3 significant figures. So when we multiply these together. x 151471.2224 We can only keep 3 significant figures 151,000

23. Significant Figures with Addition/Subtraction and Multiplication/Divison  What is the procedure when the problem requires you multiply/divide as well as add/subtract?  We will wait until the very end of all calculations and then use the multiplication/division rules to determine our number of sig figs.  Example:  v = 4.2 m / s + (3.75 m / s 2 )(8.5 s) v = 36.075 m / s  v = 36 m / s

24. Dimensional Analysis The is a term given to the process for converting units from system to system, or even within the same system. You goal is to use conversion factors to cancel out the units you no longer want, and create the units for your new measurement. Some conversion factors are: 1 in = 2.54 cm 1 kg = 2.2 lbs 1 km = 0.62 mi

25. Converting Units Time to try a couple of conversions. Convert 7.35 in to cmFirst write down your given information 7.35 inThen multiply by conversion factor. X2.54 cm 1 in Notice the unit we want to go away is put on the bottom so it divides out! Now multiply/divide the numbers as shown. 18.669 Label with the units that are left over. cm Don’t forget significant figures! 18.7 cm

26. Another Example Try one that is a little tougher and involves multiple steps. Convert 75 mph to m/s. 75 mph1 km 0.62 mi 1000 m 1 km 1 h 60 min 1 min 60 s xxxx =33.60215 34 m / s

27. Physics Lingo SymbolPronouncedMeaning  delta change; Final - Initial tt change in time; delta t time interval  Sigma sum; net; total xixi x-initialinitial position xfxf x-finalfinal position

28. Vector v Scalar  A vector quantity is any measured or calculated quantity that has: 1.Magnitude – Number found on a measuring scale or calculator 2.Direction – N,E,S,W,NE,NW,etc. or an angled direction –40 o  A scalar quantity is any measured or calculated quantity that has: 1.Magnitude – ONLY!  A scalar quantity is typically a quantity that can be counted –ie: People, money, time, etc