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Lecture 2: Introduction to Physics 101

Lecture 2: Introduction to Physics 101. Chapter 1 : The Conversion of Units (1.3) Trigonometry (1.4) Scalars and Vectors (1.5). Length:. Distance Length (m) Radius of visible universe 1 x 10 26 To Andromeda Galaxy 2 x 10 22 To nearest star 4 x 10 16

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Lecture 2: Introduction to Physics 101

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  1. Lecture 2: Introduction to Physics 101 Chapter 1 : • The Conversion of Units (1.3) • Trigonometry (1.4) • Scalars and Vectors (1.5)

  2. Length: DistanceLength (m) Radius of visible universe 1 x 1026 To Andromeda Galaxy 2 x 1022 To nearest star 4 x 1016 Earth to Sun 1.5 x 1011 Radius of Earth 6.4 x 106 Sears Tower 4.5 x 102 Football field 1.0 x 102 Tall person 2 x 100 Thickness of paper 1 x 10-4 Wavelength of blue light 4 x 10-7 Diameter of hydrogen atom 1 x 10-10 Diameter of proton 1 x 10-15

  3. Time: IntervalTime (s) Age of universe 5 x 1017 Age of Grand Canyon 3 x 1014 32 years 1 x 109 One year 3.2 x 107 One hour 3.6 x 103 Light travel from Earth to Moon 1.3 x 100 One cycle of guitar A string 2 x 10-3 One cycle of FM radio wave 6 x 10-8 Lifetime of neutral pi meson 1 x 10-16 Lifetime of top quark 4 x 10-25

  4. Mass: ObjectMass (kg) Milky Way Galaxy 4 x 1041 Sun 2 x 1030 Earth 6 x 1024 Boeing 747 4 x 105 Car 1 x 103 Physics Student 7 x 101 Dust particle 1 x 10-9 Top quark 3 x 10-25 Proton 2 x 10-27 Electron 9 x 10-31 Neutrino 1 x 10-38

  5. Conversion of Units • Example: Distance Buffalo – Andromeda Nebula given in ly. What is the distance in km ? 1. Conversion factor: 1 ly=9.5 x 1012 km 2. Insert conversion factor: d= 2 x 106 ly = 2 x 106 x 1 ly = 2 x 106 x 9.5 x 1012 km = 1.9 x 1019 km Remember: 10a x10b = 10a+b 10a/10b = 10a-b

  6. Example: • Speed limit on german autobahn is 130 kmh. What is the speed limit in mph ?

  7. correct Lecture 2, ACT 1 A very good fastball pitcher can throw the ball 100 mph. What is the ball speed in m/s? 1 - 450 m/s 2 - 45 m/s 3 - 0.045 m/s

  8. Dimensional Analysis • Dimension indicates the nature of a physical quantity or the type of unit. Example: Dimension of distance is length : [L] Unit of distance is m , km, miles, … Note: Dimensions of left-hand side and right-hand side of an equation have always to be the same, e.g. when you start with a quantity of dimension length you have to finish with one of dimension length. Powerful check of your computation !

  9. Example: • x= ½ a tn. Find n ?

  10. Trigonometry Right angle: Definition of sine, cosine and tangent: Sin q = ho/h Cos q = ha/h Tan q = ho/ha Pythagorean Theorem: h2 = ho2 + ha2

  11. Example: • A certain mountain road is inclined 3.1 degrees with respect to the horizon. What is the change in altitude (in meters) of the car as a result of its traveling 2.90 km along the road ?

  12. Scalars and Vectors

  13. Lecture 2: • Units • Dimensional Analysis • Trigonometry • Scalars and Vectors I strongly suggest that you try the example problems in the textbook. If you have trouble with any of them, please go to office hours for help!

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