Chapter 1 The Science of Physics

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

Definition of Physics Physics is the study of the physical world. Physics can be used to explain every object and phenomena around you.

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

Accuracy v Precision Accuracy is Precision 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.

Significant Figures 0 is a significant figure under certain conditions In order to be accurate and precise with our measurements, we must pay attention to significant figures while analyzing data on the calculator. It is used after a decimal point to show accuracy of measurement The numbers count as significant figures 1 2 4.2300 8 4 0 is a significant figure under certain conditions It is trapped between other significant figures. 3 6 2804 It is used as a place holder between significant figures and the decimal. 7 5 9 0 is not a significant figure if 430 .0222

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! 325.86 When we add those together 330 We can only keep to the tens place.

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 x 27.1 Has 3 significant figures. 151471.2224 So when we multiply these together. 151,000 We can only keep 3 significant figures

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 Hypothesis Make an educated guess for an answer to your question Gather information that would lead to you to a question. Conclusion Experiment Make a final statement based on your findings to prove your hypothesis. Perform an experiment and collect data to support 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 for 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 for Systeme International. Quantity Unit Length meter (m) Mass kilogram (kg) Temperature kelvin (K) Time second (s) Current ampere (A) Energy joule (J) Force newton (N)

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?

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. vlight = 299,792,458 m/s v = fλ λ = 1 / 299,792,458

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.

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.

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 1 oC = 9/5(oF) + 32

Prefixes Prefix Symbol Number pico- p .000000000001 nano- n .000000001 micro- μ .000001 milli- m .001 centi- c .01 deci- d .1 kilo- k 1000 mega- M 1,000,000 giga- G 1,000,000,000

Converting Units Time to try a couple of conversions. Convert 7.35 in to cm First write down your given information 7.35 in X 2.54 cm 1 in Then multiply by conversion factor. Notice the unit we want to go away is put on the bottom so it divides out! 18.669 cm Now multiply/divide the numbers as shown. 18.7 cm Label with the units that are left over. Don’t forget significant figures!

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

Interesting Facts Measurement Value One light-year 1 x 1025 m Mean distance from Earth to Moon 4 x 108 m Mean radius of Earth 6 x 106 m Size of cells of most living organisms 1 x 10-5 m Diameter of a proton 1 x 10-15 m Average age of a college student 6 x 108 s Time between normal heartbeats 8 x 10-1 s Duration of a nuclear collision 1 x 10-22 s

Building Blocks of Matter We all know that matter is made of many small particles called atoms. We also know that atoms are made of even smaller particles called protons, neutrons, and electrons. But what are protons, neutrons, and electrons made of?

Quarks Quarks are particles that make up the more commonly known particles called protons, neutrons, and electrons. There are six particles that are defined as quarks. They are named as follows: Up Down Strange Charmed Bottom Top The up, charmed, and top quarks have a charge +2/3 that of a proton. So a proton consists of two up quarks and one down quark. The down, strange, and down quarks have a charge of –1/3 that of a proton. A neutron consists of two down quarks and one up quark.

Coordinate Systems We are able to model position and distance by using a coordinate system to graph our model. There are two types of systems Cartesian coordinate X-Y Axis Plane polar

Plane Polar A plane polar system only needs an origin and a line of reference. The coordinates for any point refer to the distance from the origin and the angle of rotation from the line of reference. A counter-clockwise rotation gives a positive angle of rotation. A clockwise rotation gives a negative angle of rotation. The coordinates are labeled… (r , θ) where r is the distance from the origin and θ is the angle of rotation.

Converting Between Systems Knowing the polar coordinates, we can convert using one simple transformation (r , θ)  (r cos θ , r sin θ)  (x , y) Knowing the Cartesian coordinates, the transformation is a little more complicated (x , y)  (√x2+y2 , tan-1 y/x)  (r , θ)