Chapter 1 Key Objectives Definition of Physics Areas of Physics What is the Scientific Method
Peterson, Diane, Food Writer has reference to this Academic Journal, PHwiki organized this Journal Chapter 1 The Science of Physics Key Objectives Definition of Physics Areas within Physics Scientific Method Measurements in addition to Units (SI) Accuracy in addition to Precision Dimensional Analysis Definition of Physics Physics is the study of the physical world. A science that deals with matter in addition to energy in addition to 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 as long as th Merriam-Webster Online Dictionary Physics can be used to explain every object in addition to phenomena around you.
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Areas of Physics Mechanics Thermodynamics Vibrations in addition to Waves Optics Electromagnetism Relativity Quantum Mechanics Motion in addition to its causes Heat in addition to Temperature Specific types of repetitive motion Light Electricity, Magnetism, & Light Particles moving at high speeds Behavior of submicroscopic particles 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 in as long as mation that would lead to you to a question. Hypothesis Experiment Make an educated guess as long as an answer to your question Conclusion Per as long as m an experiment in addition to collect data to support your hypothesis. Make a final statement based on your findings to prove your hypothesis. Units of Measurement There are many different systems of measurements in science. Here in the United States, we use the English system of units. miles pounds Fahrenheit Other countries, such as Canada, use the Metric system of units. meter gram Celsius Since the world cannot decide on what units to use, scientists have. We have come to a mutual agreement as long as a consistent system of units
SI Units That mutual system is called the International System of units. We abbreviate it using SI, which is short as long as Systeme International. Length meter (m) Mass kilogram (kg) Temperature kelvin (K) Time second (s) Current ampere (A) Energy joule (J) Force newton (N) St in addition to ards of Length, Mass, in addition to Time We all know these are used to measure certain characteristics of the phenomena around us. Be as long as e we knew of things such as the meter, or kilogram, or second, the quantities above had no st in addition to ard way of being measured. So how did we come to designate a certain distance, or time interval, or mass as being the st in addition to ards as long as all measurements These 3 are a few examples of SI Base Units because they st in addition to alone without deriving the units of measure from any other unit. The Kilogram The kilogram is defined as the mass of a specific platinum-iridium alloy cylinder kept as the International Bureau of Weights in addition to 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.
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 St in addition to ards in addition to 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. vlight = 299,792,458 m/s v = f = 1 / 299,792,458 The Second Be as long as e 1960, the time st in addition to ard 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. Prefixes pico- nano- micro- milli- centi- deci- kilo- mega- giga- p n m c d k M G .000000000001 .000000001 .000001 .001 .01 .1 1000 1,000,000 1,000,000,000
Example 1.1 Give the numerical equivalent to the following measurements using the appropriate prefix. 36 nanometers 36 nm 463 kiloseconds 463 ks 86 micrograms 86 g .1495 megajoules .1495 MJ Example 1.2 Give the decimal equivalent to the following measurements in their base unit. 7 dm 7 x 10-1 m 0.7 m 38 Gs 38 x 109 s 38,000,000,000 s 423 pJ 423 x 10-12 J .000 000 000 423 J 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 in addition to precise in our measurements.
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 Significant Figures In order to be accurate in addition to precise with our measurements, we must pay attention to significant figures while analyzing data on the calculator. The numbers 1 2 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 4.2300 It is trapped between other significant figures. 2804 0 is not a significant if It is used as a place holder between significant figures in addition to the decimal. 430 .0222 Example 1.3 Identify the number of significant figures found in the following measurements. 203 mi 3 sig figs .0048 m 2 sig figs 7700 kg 2 sig figs 3.45 x 106 N 3 sig figs 981.0 ± 0.1 s 4 sig figs Ignore the tolerance value of 0.1
Scientific Notation to the Rescue What happens when the answer is rounded up or down to zero, in addition to 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 103 m 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 Multiplication & Division Finding how many significant figures to keep with multiplication in addition to division is much easier than with other operations. That is because you simply count how many significant figures are in each measurement, in addition to 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. 151471.2224 We can only keep 3 significant figures 151,000
Significant Figures with Addition/Subtraction in addition to 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 in addition to then use the multiplication/division rules to determine our number of sig figs. Example: v = 4.2 m/s + (3.75 m/s2)(8.5 s) v = 36.075 m/s v = 36 m/s Dimensional Analysis The is a term given to the process as long as 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, in addition to create the units as long as your new measurement. Some conversion factors are: 1 in = 2.54 cm 1 kg = 2.2 lbs 1 km = 0.62 mi Converting Units Time to try a couple of conversions. Convert 7.35 in to cm First write down your given in as long as mation 7.35 in Then multiply by conversion factor. X 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 Dont as long as get significant figures! 18.7 cm
Another Example Try one that is a little tougher in addition to involves multiple steps. Convert 75 mph to m/s. 75 mph 1 km 0.62 mi 1000 m 1 km 1 h 60 min 1 min 60 s = 33.60215 34 m/s Physics Lingo Vector v Scalar A vector quantity is any measured or calculated quantity that has: Magnitude Number found on a measuring scale or calculator Direction N,E,S,W,NE,NW,etc. or an angled direction 40o A scalar quantity is any measured or calculated quantity that has: Magnitude ONLY! A scalar quantity is typically a quantity that can be counted ie: People, money, time, etc
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