1. 1 HONORS 227 1 September 2015 Dr. Harold Geller College of Science School of Physics, Astronomy and Computational Sciences George Mason University

2. 2 Chapters 1 and 2 and Other Stuff A Personal Response System (iClickers) Units of length, mass and time Metric Prefixes Chapter 2 and the Ordered Universe

3. 3 iClicker Qustion The pyramids were built by extraterrestrials from outer space. AAgree BDisagree

4. 4 iClicker Qustion The location of the stars and planets at birth determine your personality. AAgree BDisagree

5. 5 iClicker Qustion Humans have never stepped foot on the Moon’s surface. AAgree BDisagree

6. 6 The basic unit of angular measure is the degree (°).

7. 7 Angular Measurements Subdivide one degree into 60 arcminutes –minutes of arc –abbreviated as 60 arcmin or 60´ Subdivide one arcminute into 60 arcseconds –seconds of arc –abbreviated as 60 arcsec or 60” 1° = 60 arcmin = 60´ 1´ = 60 arcsec = 60”

8. 8 iClicker Question How many arcseconds are there in a degree? A60 arcseconds B360 arcseconds C3600 arcseconds D600 arcseconds EThese are incompatible units.

9. 9 Powers-of-ten notation is a useful shorthand system for writing numbers

10. 10 iClicker Question Which measurement of an average classroom door is closest to 2 meters? A.Thickness B.Width C.Height D.Surface area E.Volume

11. 11 iClicker Question What is the result if you multiply 10 15 by 10 10 ? A10 15 B10 10 C10 150 D10 25 E2 x 10 15

12. 12 iClicker Question What is the result if you add 10 15 to 10 15 ? A10 15 B10 30 C10 150 D10 25 E2 x 10 15

13. 13 iClicker Question What is the result if you multiply 10 15 by 10 15 ? A10 15 B10 30 C10 150 D10 225 E2 x 10 15

14. 14 Common Prefixes for Powers of Ten FactorNameSymbol (billion) 10 9 Giga-G (million) 10 6 Mega-M (thousand) 10 3 kilo-k (hundredth) 10 -2 centi-c (thousandth) 10 -3 milli-m (millionth) 10 -6 micro-  (billionth) 10 -9 nano-n

15. 15 Astronomical distances are often measured in astronomical units, lightyears or parsecs Astronomical Unit (AU) –One AU is the average distance between Earth and the Sun –1.496 X 10 8 km or 92.96 million miles Light Year (ly) –One ly is the distance light can travel in one year at a speed of about 3 x 10 5 km/s or 186,000 miles/s –9.46 X 10 12 km or 63,240 AU Parsec (pc) –the distance at which 1 AU subtends an angle of 1 arcsec or the distance from which Earth would appear to be one arcsecond from the Sun –1 pc = 3.09 × 10 13 km = 3.26 ly

16. 16 iClicker Question Which unit of the following is the largest? AKilometer BAstronomical Unit (AU) CLight Year (ly) DParsec (pc) EGigameter

17. 17 Science is an adventure of the human mind

18. 18 HNRS 227 Chapter 2 – Ordered Universe

19. 19 Main Concepts I will focus Upon from Chapter 2 Speed vs. Velocity Acceleration Force Falling Objects Newton’s Laws of Motion Momentum Angular Momentum Universal Law of Gravity

20. 20 Speed and Velocity Speed –distance traveled in a unit of time –a scalar quantity Velocity –speed and direction –a vector quantity

21. 21 iClicker Question What is the difference between speed and velocity? ASpeed is a vector and velocity is a scalar quantity. BSpeed is a scalar and velocity is a vector quantity. CThere is no difference between speed and velocity. DAll of the above are true statements.

22. 22 Questions for Thought What is acceleration? AThe change in distance per change in time. BThe change in position per unit of time. CThe ratio of the change in velocity per change in time. DThe change of time per unit of length.

23. 23 Questions for Thought An insect inside a bus flies from the back toward the front at 5.0 miles/hour. The bus is moving in a straight line at 50 miles/hour. What is the speed of the insect? AThe speed of the insect is 5 miles per hour relative to the bus. BThe speed of the insect is 55 miles per hour relative to the ground. CThe speed of the insect is 50 miles per hour relative to the ground. DBoth A and B above are true. EA, B and C above are true.

24. 24 Force Definition of force –something that causes a change in the motion of an object a push or pull an electric, magnetic, gravitational effect a vector quantity Net force - Resultant Force

25. 25 Inertia Defining Inertia –tendency of an object to remain in its current state of motion the more massive the more inertia think of stopping a car vs. truck

26. 26 Acceleration Due to Gravity Direction of acceleration due to gravity –directed to center of Earth Think: scalar or vector? –a vector quantity Why? –has magnitude and direction

27. 27 Generalized Motion Motion can be viewed as a combination of movements –vertical component typically gravitational acceleration –horizontal component some force from muscle, gunpowder, etc.

28. 28 Question for Thought What happens to the velocity and acceleration of an object in free fall? AThe velocity decreases as the acceleration remains the same. BThe velocity increases as the acceleration remains the same. CThe velocity increases and the acceleration decreases. DThe velocity increases and the acceleration increases. EBoth velocity and acceleration decrease.

29. 29 Question for Thought In the equation d=1/2*a*t 2, if a is 9.8 meters per second per second and t is in seconds, what is the unit of d? Aseconds Bmeters Ckilometers Dfeet per second Emeters per second

30. 30 Question for Thought Do you recall what inertia is? Inertia is the property of matter that an object will remain in unchanging motion or at rest in the absence of an unbalanced force.

31. 31 Question for Thought Where does the unit s 2 (or concept of “square second”) come from? Acceleration is change in velocity per change in time, with units of (m/s)/s. When the fraction is simplified, you get meters per second squared. The “seconds squared” indicates that something that changes in time is changing in time, that is, the ratio of change in distance per unit of time is changing in time.

32. 32 Question for Thought Neglecting air resistance, what are the forces acting on a bullet after it has left the barrel of a rifle? –AThe force of air acting up and gravity acting down. –BOnly the force of gravity acting straight down. –CThere are no forces acting at this point. –DAll of the above are true.

33. 33 Question for Thought How does the force of gravity on a ball change as a ball is thrown straight up in the air? AThe force of gravity increases. BThe force of gravity decreases. CThe force of gravity remains the same. DThe force of gravity increases then decreases. EThe force of gravity decreases then increases.

34. 34 Sample Question An object falls from a bridge and hits the water 2.5 seconds later. –A) With what velocity did it strike the water? –B) What is the average velocity during the fall? –C) How high is the bridge?

35. 35 Sample Answer

36. 36 Newton’s Laws of Motion Newton’s First Law of Motion –body at rest tends to stay at rest and body in uniform motion will stay in straight line uniform motion unless acted upon by an outside force Newton’s Second Law of Motion –the acceleration of a body is proportional to the force being applied –F = m*a

37. 37 Newton’s Laws of Motion Newton’s Third Law of Motion –for every force there is an equal and opposite force (action and reaction)

38. 38 Question for Thought How can there ever be an unbalanced force on an object if every action has an equal and opposite reaction? The action and reaction forces are between two objects that are interacting. An unbalanced force occurs on a single object as the result of one or more interactions with other objects.

39. 39 Sample Question What force would an asphalt road have to be to give a 6,000 kilogram truck in order to accelerate it at 2.2 meters per second per second?

40. 40 Sample Question Answer

41. 41 Momentum By definition momentum is the product of – mass and velocity Conservation of momentum –total momentum of a closed system remains constant

42. 42 Question for Thought Is it possible for a small car to have the same momentum as a large truck? –AYes –BNo Yes, the small car would have to be moving with a much higher velocity, but it can have the same momentum since momentum is mass times velocity.

43. 43 Angular Momentum Torque –Twisting force Conservation of Angular Momentum –“an object that is rotating will keep rotating unless a twisting force called a torque acts to make it stop” –Applications include Ice skater Inertial guidance systems

44. 44 Universal Law of Gravity Newton’s Universal Law of Gravitational Attraction –every object is attracted to every other object –the force is proportional to masses and inversely proportional to the distance squared »F = (G*m*M) / r 2

45. 45 A Problem of Very Little Attraction What is the gravitational force between two 100 kilogram people separated by 1 meter?

46. 46 Really just a little Use the formula for the force of gravity: F = G*m*M / r 2 where G = 6.67 x 10 -11 Nm 2 /kg 2 and m = 100 kg and M = 100 kg and r = 1 ======================= Then F = 6.67 x 10 -11 Nm 2 /kg 2 *100 kg*100 kg / (1 meter) 2 F = 6.67 x 10 -7 N