1. PHY 110, Introduction to Physics Dr. Henry SC 453, 572-6164 (alt 572-5309) E-Mail: henryh1@nku.eduhenryh1@nku.edu Web Site: www.nku.edu/~henryh1/ © Hugh Henry, 2008 Do not leave Voice Mail Messages Use E-Mail Instead

2. PHY 110, Introduction to Physics Dr. Henry SC 453, 572-6164 (alt 572-5309) © Hugh Henry, 2008

3. PHY 110, Introduction to Physics “Physics is either impossible or trivial. It is impossible until you understand it... then it becomes trivial.” – Ernest Rutherford (1871-1937)

4. PHY 110, Introduction to Physics Rutherford also said: “In science there is only physics; everything else is stamp collecting.”

5. PHY 110, Introduction to Physics Rutherford’s comments are related: Physics is logic – not memorization Physics is a Way of Thinking that may be unfamiliar –But when you catch on, it’s much easier!!

6. Textbooks (Inquiry into) Physics Ostdiek and Bord 1 st Edition ( 2011-2011 )

7. Textbooks 6 th Edition (left) and 5 th Edition (right) Almost Identical – OK If You Can Get them Cheap

8. Lab Manual Posted in Blackboard as pdf files Students are expected to download and print prior to each lab session. One lab report per group of 3-5 students Lab report includes graphs –Graph paper 10x10 per inch (or finer) must be obtained and brought to lab sessions. (Available at cost in lab.)

9. Course Syllabus is available online http://www.nku.edu/~henryh1/Syllabus.htm OR NKU’s Blackboard System

10. Syllabus Questions?? “Students are responsible to read and understand all items on this syllabus before the first class. “Any items not understood must be brought to the attention of the instructor within the first two weeks of class. “THE SYLLABUS WILL NOT BE REVIEWED OR DISCUSSED IN CLASS, EXCEPT TO ANSWER QUESTIONS.”

11. Course Essentials Online Honor Quiz every 2 weeks (approx) Midterm and Final Exams are proctored Quizzes and Exams are curved No lab makeups – but Tuesday students can come Thursday (and vice versa) –90% class attendance  1 free lab cut Up to 5% extra credit is allowed Students must check Blackboard at least weekly for assignments and lab download

12. Course Essentials Grading based on: Honor Quiz Average – 28% Midterm Exam – 27% Final Exam – 35% Lab grade – 10% Extra credit is added to student’s net score

13. 13 Personal Responsibility This is America! – you can accomplish whatever you set your mind to do –... but you have to work at it There are no victims in this class –Everyone will be equally abused without regard to race, religion, sexual preference, or socioeconomic background Grading is based strictly on tests and labs –Plus any Extra Credit work (good for up to 5 points added to your final grade)

14. If you are Tardy Initial beside Your Name on the Sheet on the Front Table

15. Introduction

16. 16 Superconductivity Medical Physics: Ultrasound/Radiation Oncology My Background

17. Physics Helps Us Understand the World around Us

18. 18 Physics is all around us

19. 19 Acceleration

20. 20 Deceleration

21. 21 Golf and Tennis use Physics

22. 22 Pool uses Physics

23. 23 Physics on Ice

24. 24 Football uses Physics

25. 25 Space Program based on Physics

26. 26 Physics Helps Understand the World Around Us

27. BP Oil Leak Why was it so hard to “Plug the damn hole” (Pres Obama) at the BP Deep Water Horizons Oil leak in 2010? We will learn as we study chapter 4. Physics helps us understand the world around us

28. Modern Physics is a very new Science A brief look at the history of Physics...

29. Physics Began with the Ancient Greeks Greek “science” was philosophy – ignoring experimentation and mathematics – even though the Greeks developed geometry. Democritus and Leuccipus and proposed atomic theory in the 5 th century BC Thales of Miletus 624-546 BC Pythagoras of Samos 570-500 BC Democritus of Abdera 460-370 BC

30. 30 Plato (427-347 BC) Aristotle (384-322 BC) Aristotle’s philosophy dominated “physics” until Galileo and Newton The School of Athens, Raphael

31. The Middle Ages After the Roman Empire fell, the West plunged into what is called the “Dark Ages,” and Greek science was forgotten. Aristotle’s physics was “rediscovered” in the West ~1000 AD. Thomas Aquinas (1225-1274) incorporated it into Roman Catholic theology – including the geocentricity principle. –The Sun and planets circle the Earth 31

32. The Protestant Reformation The 16 th century Protestant Reformation encouraged scientific inquiry Nature was no longer believed shrouded in mystery –“Since the creation of the world God’s invisible qualities... have been clearly seen... from what has been made” (Romans 1:20) 32 Martin Luther’s 95 Theses, 1517

33. 33 Galileo, 1564-1642 Galileo Pioneered Experimental Physics

34. 34 Galileo Pioneered Experimental Physics The science of the ancient Greeks involved thinking about the way the world works Galileo did experiments to see how the world really works.

35. Aristotle... Wrong on Gravity Aristotle “didn’t do silly experiments, but proved truth with impeccable logic.”* He believed a large ball would fall to earth faster than a small ball. A simple experiment would have falsified this theory. It took almost 2000 years before Galileo finally did this experiment. With Galileo, much of Aristotle’s physics begins to fall apart. Aristotle (384-322 BC) *Marshall Brucer, A Chronology of Nuclear Medicine (St. Louis: Heritage Publicationss, 1990) 8.

36. 36 Experiment is Modern Physics’ Gold Standard Galileo’s Incline Plane Experiment

37. Aristotle... Wrong on The Planets Copernicus and Galileo demonstrated from observation and mathematics that the Earth and the planets circle the Sun. Aristotle (384-322 BC)

38. 38 Inquisition of Galileo, 1633 AD Yet 17 th century scientists believed Aristotle that the Sun circled the Earth; they scorned Galileo’s Mathematics and Observation

39. “Settled Science” The next time you hear a claim that “99% of scientists agree” or that something is “Settled Science,” remember Galileo! 99% of 17 th century scientists thought the sun circled the Earth. Science is not determined by majority vote – and those who make such claims do so as a substitute for scientific proof. “Methinks the lady doth protest too much” – Shakespeare

40. 40 Sir Isaac Newton, 1642-1727 Father of Experimental Research

41. 41 Since Experimental Physics is Relatively Recent, so are Most Key Principles of Physics: Settlement of Jamestown: 1607 Newton’s Principia (Chapter 2) ~1687 American Revolution: 1776-1781 Electromagnetism (Chapter 8) ~1830 Conservation of Energy (Chapter 3) and Laws of Thermodynamics (Chapter 5) ~1850 American Civil War 1861-1865 Relativity (Chapter 12) ~1910

42. 42 Albert Einstein, 1879-1955 E=mc 2 Relativity

43. 43 Person of the Century

44. The Electronics Modern People Take for Granted was Mostly Developed over Our Lifetimes

45. 45 Slide Rule This was the “computer” used by scientists into the 1970’s –I did most of my Ph.D. work with a slide rule

46. 46 Punchcard Computers 1960’s

47. 47 1970 PDP 11 Computer

48. 48 1972 HP 35 Hand-held, “Electronic Slide Rule”

49. 49 Later 70’s Solar Cells (Cheap Calculators) Modern TI BA35

50. Most Advances in Physics have Happened in Our Lifetimes

51. Physics is a Way of Thinking

52. 52 Modern Scientific Method OR Observation Explanation Feedback Hypothesis Experiment Analysis Feedback

53. 53 Ask Questions Seek Answers Question the Answers Question the Questions

54. 54 Practical Scientific Method

55. 55

56. Using the Scientific Method Helps Differentiate Real Science from Trans-Science and Politicized Science

57. Beware the “Scientific- Technological Elite” money is ever present – and is gravely to be regarded.... We must also be alert to the... danger that public policy could itself become the captive of a scientific- technological elite.” President Eisenhower's Farewell Address to the Nation January 17, 1961 http://www.informationclearinghouse.info/article5407.htm “The prospect of domination of the nation's scholars by Federal employment, project allocations, and the power of

58. 58 Alvin Weinberg’s “Trans-Science” “Questions that can be stated in scientific terms but that are... beyond the proficiency of science to answer”... [are] “Trans-Scientific” Alvin Weinberg, Science, 177:211 (21 July 1972)

59. 59 Ask Questions Seek Answers Question the Answers Question the Questions Use your intellect... follow the scientific method of logical analysis in all areas of life

60. Chapter 1 The Study of Motion © Hugh Henry, 2008

61. Measurement is an Essential Part of the Scientific Method In order to analyze a system scientifically, it must be measurable and quantitative information obtained

62. 62 Qualitative vs Quantitative Mathematics vs Philosophy “Tall” or 6’8” “Far” or 1896 miles “Fast” or 145 mph

63. 63 Furthermore, to communicate quantitative information, there must be consistency of units

64. 64 Some Different Units Used to Measure Distance 241 kilometers 241,402 meters

65. Magna Carta, 1215 The Great Charter Included standardized weights and measures among rights granted Englishmen by King John

66. Inconsistent Units and Christopher Columbus Columbus’ Big Miscalculation: 15 th century scholars did NOT think the world was flat But Columbus underestimated the Earth’s circumference by ~36% because he thought an astronomer’s calculation of 20,400 miles was in Italian miles (~1.238 km) – but it was in Arabic miles (~1.830 km). The real circumference is 24,902 English miles (1.610 km/mile): 40,076 km

67. 67 Fundamental Physical Quantities Distance: d Time: t Mass: m

68. 68 Units We can classify almost all quantities in terms of the fundamental physical quantities: Distanced Massm Timet For example:  Speed has units d/t (miles per hour)

69. 69 Unit Consistency We will discuss three standards of units: Metric Units: SI (Système International) Units: d = meters (m) m = kilograms (kg) t = seconds (s) CGS Units: d = centimeters (cm) m = grams (g or gm) t = seconds (s)

70. 70 Unit Consistency, cont’d British (or English) Units: d = feet (ft) m = slugs or pound-mass (lbm) t = seconds (s) We will use mostly SI but we need to know how to convert back and forth.

71. 71 British vs Metric (SI) Systems Inches, Feet, Miles Hours, Minutes, Seconds Slugs Centimeters, Meters, Kilometers Hours, Minutes, Seconds Milligrams, Grams, Kilograms

72. 72 Fundamental Physical Quantities Distance: d Time: t Mass: m

73. Distance

74. 74 Converting units The “Special Review Card” in the back of the textbook provides numerous conversions. Here are some of them: 1 inch=2.54 cm 1 m= 3.281 ft 1 mile=5280 ft 1 km=0.621 mi

75. 75 Converting units, cont’d Here is the procedure to convert units: Look at your original units. Determine the units you want to have. Find the conversion factor(s) you need. Multiply the original unit by a fraction equal to one (1) that the net effect of replacing the original unit with the desired new unit. The following examples illustrate this principle

76. 76 Example A yacht is 20 m long. Express this length in feet. ANSWER:

77. 77 Example It may be necessary to do this more than once: How many liters are in a five gallon bucket? There are four quarts in a gallon. ANSWER:

78. 78 Converting units, cont’d We can use this principle to convert a compound unit through successive multiplications by one (1):

79. British and Metric (SI) Systems Non-Decimal vs Decimal

80. 80 Metric prefixes Sometimes a unit is too small or too big for a particular measurement. To overcome this, we use a prefix.

81. 81 millimeters vs kilometers

82. 82 Metric prefixes, cont’d Power of 10PrefixSymbol 10 15 petaP 10 12 teraT 10 9 gigaG 10 6 megaM 10 3 kilok 10 -2 centic 10 -3 millim 10 -6 micro  10 -9 nanon 10 -12 picop 10 -15 femtof

83. 83 Metric prefixes, cont’d Some examples: –1 centimeter= 10 -2 meters = 0.01 m –1 millimeter = 10 -3 meters = 0.001 m –1 kilogram= 10 3 grams = 1,000 g

84. 84 deci... centi... milli

85. Scientific Notation If you don’t know it already, learn it now!

86. 86 Express large or small numbers as powers of 10 2,210,000,000,000  2.21 * 10 12 0.0000000789  7.89 * 10 -8 Many of you will try to work with these numbers using a hand-held calculator –But it’s more reliable to do it the “old-fashioned” way (2.21 * 10 12 ) * (7.89 * 10 -8 )  2.21 * 7.89 * 10 12-8  17.4369 * 10 4  1.74369 * 10 5

87. Significant Figures Round off the above answer: 1.74369 * 10 5  1.744 * 10 5 OR 1.74 * 10 5

88. 88 Laboratory Exercises: Data Analysis Taking the Data Charting the Data Graphing the Data

89. 89 Graphing the Data Independent Variable on “X” Axis Dependent Variable on “Y” Axis $0.80

90. 90 Graphing Non-linear Data Data not on a straight line

91. 91 Experimental Error For a variety of reasons – precision of setup, human error, etc – data measured in laboratory exercises will be in error Calculate “Experimental Error”: Experimental Error = 100% * (d c – d m )/d c where d c is correct data, d m is measured data

92. 92 Fundamental Physical Quantities Distance: d Time: t Mass: m

93. 93 Frequency and period We define frequency as the number of events per a given amount of time. When an event occurs repeatedly, we say that the event is periodic. The amount of time between events is the period.

94. Frequency The number of cycles of a periodic process that occur per unit time Standard unit: Hertz (Hz) = 1/s

95. Period Period is the time for one complete cycle for a process that repeats It is abbreviated T, and the units are time units

96. 96 Frequency and period, cont’d The symbols we use to represent frequency and period are: frequency: f period: T They are related by

97. 97 Frequency and period, cont’d The standard unit of frequency is the Hertz (Hz). It is equivalent to 1 cycle per second.

98. 98 Example Example 1.1 A mechanical stopwatch uses a balance wheel that rotates back and forth 10 times in 2 seconds. What is the frequency of the balance wheel? ANSWER:

99. 99 The pendulum in this clock rotates back and forth 10 times in 20 seconds ANSWER: T = 20 s/10 cycles = 2 s What is the period of the pendulum?

100. Defining the Meter A meter is defined as one ten-millionth of the length of the Earth’s meridian along a quadrant. The dimensions of the Earth were known many, many years ago An early definition was the length of a pendulum with a half-period of 1 second. T = 2 sec f = 0.5 Hz The period of a pendulum will be discussed in chapter 2

101. 101 Fundamental Physical Quantities Distance: d Time: t Mass: m

102. Mass vs Weight Weight Mass

103. 103 Fundamental Physical Quantities Distance: d Time: t Mass: m

104. 104 Other Physical Quantities are Derived (Calculated) from d, t, m Speed: v = d/t Frequency: f = 1/t (1/T) Weight: w= mg

105. 105 Speed Speed is the rate of change of distance from a reference point. It is the rate of movement. It equals the distance something travels divided by the elapsed time.

106. Speed

107. 107 Speed, cont’d In mathematical notation, So we can write speed as

108. Change in Distance (d) Change in Time (t) Speed (v) = = (d f - d i ) / (t f - t i ) =  d /  t

109. 109 Average vs Instantaneous Speed The symbol  is the Greek letter delta and represents the change in. As the time interval becomes shorter and shorter, we approach the instantaneous speed. Avg vs Instant Speed

110. Calculate Average Speed of Flo Jo in the 100 meter dash Avg Speed = Δd / Δt = (d f - d i ) / (t f - t i ) = 100 – 0 m / 10.5 – 0 s = 100 m / 10.5 s = 9.52 m/s

111. Calculate Her Average Speed over the last 40 meters Avg Speed = Δd / Δt = (d f - d i ) / (t f - t i ) = 100 – 60 m / 10.5 – 6.85 s = 40 m / 3.65 s = 10.96 m/s

112. 112 Speed, cont’d If we know the average speed and how long something travels at that speed, we can find the distance it travels:

113. 113 Speed, cont’d We say that the distance is proportional to the elapsed time: Using the speed gives us an equality, i.e., an equal sign, so we call v the proportionality constant.

114. 114 Speed of Sound and Speed of Light d = vt  v = d/t

115. 115 Example When lightning strikes, you see the flash almost immediately but the thunder typically lags behind. The speed of light is 3 × 10 8 m/s and the speed of sound is about 345 m/s. If the lightning flash is one mile away, how long does it take the light and sound to reach you?

116. 116 ANSWER: For the thunder: For the flash: Example

117. 117 Speed, cont’d Note that speed is relative. It depends upon what you are measuring your speed against. Consider a woman running at 8 mph on a ship moving at 20 mph.

118. 118 Speed, cont’d If you are clocking her speed on the ship, you see her moving at

119. 119 Speed, cont’d If you are clocking her speed on the dock, she is moving at

120. 120 Velocity This introduces the contrast between speed and velocity Velocity is the speed in a particular direction. It tells us not only “how fast” (like speed) but also how fast in “what direction.”

121. 121 Velocity, cont’d In common language, we don’t distinguish between the two. This sets you up for confusion in a physics class. During a weather report, you might be given the wind-speed is 15 mph from the west. The speed of the wind is 15 mph. The wind is blowing in a direction from the west to the east. So you are actually given the wind velocity.

122. Velocity: Speed plus Direction Speed is a “scalar” No particular direction Velocity is a “vector” Speed in a particular direction

123. 123 Vector addition Quantities that convey a magnitude and a direction, like velocity, are called vectors. We represent vectors by an arrow. The arrow represents the direction The length indicates the magnitude.

124. 124 Vector addition, cont’d Consider again the woman running on a ship. If ship and woman are in the same direction, the vectors add.

125. 125 Vector addition, cont’d Consider again someone running on a ship. If ship and woman are in opposite directions, the vectors subtract.

126. 126 Vector addition, cont’d What if the vectors are at an angle?

127. 127 Vector addition, cont’d The resulting velocity of the bird (from the bird’s velocity and the wind) is a combination of the magnitude and direction of each velocity. Plane and Wind

128. 128 Vector addition, cont’d We can find the resulting magnitude of the Pythagorean theorem. b a c

129. 129 Vector addition, cont’d This is used to find the net speed of the bird. This is for your information only; it won’t be on a test 10 8 6

130. 130 Vector addition, cont’d Here are more examples, illustrating that even if the bird flies with the same velocity, the effect of the wind can be constructive or destructive.

131. 131 Vector Addition Resultant Velocity River Boat

132. 132 Vector Addition Vector 1 = 300 miles/hour, west Vector 2 = 300 miles/hour, north Vector 3 = Vector 1 + Vector 2

133. 133 Vector Addition

134. 134 Acceleration Acceleration is the change in velocity divided by the elapsed time. It measures the rate of change of velocity. Mathematically, Acceleration vs Constant Velocity

135. 135 Acceleration, cont’d The units are In SI units, we use m/s 2.

136. 136 Gravity is an acceleration g = 9.8 m/s 2 About_Falling_Things

137. 137 Acceleration, cont’d A common way to express acceleration is in terms of g ’s. One g is the acceleration an object experiences as it falls near the Earth’s surface: g = 9.8 m/s 2. So if you experience 2 g during a collision, your acceleration was 19.6 m/s 2.

138. 138 Acceleration, cont’d There is an important point to realize about acceleration: It is the change in velocity.

139. 139 Acceleration, cont’d Since velocity is speed and direction, there are three ways it can change: change in speed, change in direction, or change in both speed & direction. The change in direction is an important case often misunderstood.

140. 140 Acceleration, cont’d We know that acceleration takes place as this car speeds. The change in velocity is Δv = v 2 – v 1 Stoplight Accel

141. 141 Acceleration, cont’d But acceleration also takes place if you drive through a curve with the cruise control set. Not because your speed changes. But because your direction is changing. You can sense acceleration if items on your dash slide around. (More on this in chapter 2.) Δv = v 2 – v 1

142. All these motions are Acceleration Hot Wheels

143. 143 Example Example 1.3 A car accelerates from 20 to 25 m/s in 4 seconds as it passes a truck. What is its acceleration?

144. 144 ANSWER: The problem gives us The acceleration is: Example Example 1.3

145. 145 CHECK: Does this make sense? The car needs to increase its speed 5 m/s in 4 seconds. If it increased 1 m/s every second, it would only reach 24 m/s. So we should expect an answer slightly more than 1 m/s every second. Example Example 1.3

146. 146 Example Example 1.4 After a race, a runner takes 5 seconds to come to a stop from a speed of 9 m/s. Find her acceleration. v = 9 m/s

147. 147 ANSWER: The problem gives us The acceleration is: Example Example 1.4

148. 148 CHECK: Does this make sense? If she was traveling at 10 m/s, reducing her speed 2 m/s every second would stop her in 5 seconds. What’s up with the minus sign? Example Example 1.4

149. 149 Negative Acceleration Means the Object is Slowing Down Like this car... avoiding the cliff

150. 150 Centripetal acceleration Remember that acceleration can result from a change in the velocity’s direction. Imagine a car rounding a curve. The car’s velocity must keep changing toward the center of the curve in order to stay on the road.

151. 151 Centripetal acceleration Ditto a ball being swung around on a tether. The ball’s velocity must keep changing toward the center to stay in the circle This acceleration is perpendicular to the velocity.

152. 152 Centripetal acceleration, cont’d So there is an acceleration toward the center of the curve. Centripetal acceleration is the acceleration associated with an object moving in a circular path. Centripetal means “center-seeking.”

153. 153 Centripetal acceleration, cont’d For an object traveling with speed v on a circle of radius r, then its centripetal acceleration is

154. 154 Centripetal acceleration, cont’d Note that the centripetal acceleration is: proportional to the speed-squared inversely proportional to the radius

155. 155 Example Example 1.5 Let’s estimate the acceleration of a car as it goes around a curve. The radius of a segment of a typical cloverleaf is 20 meters, and a car might take the curve with a constant speed of 10 m/s.

156. 156 ANSWER: The problem gives us The acceleration is: Example Example 1.5

157. 157 Example Problem 1.18 An insect sits on the edge of a spinning record that has a radius of 0.15 m. The insect’s speed is about 0.5 m/s when the record is turning at 33- 1 / 3 rpm. What is the insect’s acceleration?

158. 158 ANSWER: The problem gives us The acceleration is: Example Problem 1.18

159. 159 Centripetal Acceleration of a peregrine falcon A peregrine falcon dives vertically at a velocity of 101 m/s. It pulls out of the dive by changing direction at constant velocity over a radius of 61.2 m. What is the centripetal acceleration of the falcon in m/s 2 and g’s? a = v 2 /r = (101m/s) 2 /61.2m = 10,201(m/s) 2 /61.2m = 166.7m/s 2 a = 166.7m/s 2 / 9.8m/s 2 = 17.0 g A human would black out before reaching 5 g’s. © Hugh Henry, 2005

160. 160 Types of Motion

161. 161 Simple types of motion — zero velocity The simplest type of motion is obviously no motion. The object has no velocity. So it never moves. The position of the object, relative to some reference, is constant.

162. 162 Simple types of motion — constant velocity The next simplest type of motion is uniform motion. In physics, uniform means constant. The object’s velocity does not change. So its position, relative to some reference, is proportional to time.

163. Constant Velocity d = vt v = 9 m/s

164. 164 Simple types of motion — constant velocity, cont’d If we plot the object’s distance versus time, we get this graph. Notice that if we double the time interval, then we double the object’s distance.

165. 165 Simple types of motion — constant velocity, cont’d The slope of the line gives us the speed. Constant Rt Velocity

166. 166 Simple types of motion — constant velocity, cont’d If an object moves faster, then the line has a larger speed. So the graph has a steeper slope.

167. 167 Reading distance vs time graphs...

168. 168 Distance vs Time for Auto with Varying Velocity

169. 169 Simple types of motion — constant acceleration The next type of motion is uniform acceleration in a straight line. The acceleration does not change. So the object’s speed is proportional to the elapsed time.

170. 170 Simple types of motion — constant acceleration, cont’d A common example is free fall. Free fall means gravity is the only thing changing an object’s motion. The speed is:

171. 171 Simple types of motion — constant acceleration, cont’d If we plot the object’s speed versus time, we get this graph. Notice that if we double the time interval, then we double the object’s speed. Rt Velocity w/Rt Accel

172. 172 Simple types of motion — constant acceleration, cont’d The slope of the line is the acceleration:

173. 173 Simple types of motion — constant acceleration, cont’d For an object starting from rest, v = 0, then the average speed is

174. 174 Simple types of motion — constant acceleration, cont’d The distance is the average speed multiplied by the elapsed time:

175. 175 Simple types of motion — constant acceleration, cont’d If we graph the distance versus time, the curve is not a straight line. The distance is proportional to the square of the time.

176. 176 Distance vs Time for Freely Falling Body

177. 177 For constant acceleration: v = at is a straight line, but d = at 2 /2 is a parabola

178. 178 Non- Constant Acceleration of Gearshift Car

179. 179 Ball Thrown Straight Up Velocity in direction of motion; Acceleration (g) always down

181. 181 Summary of Important Equations

182. END