Physics 4A: Newtonian Classical Mechanics

Transcription

1 Physics 4A: Newtonian Classical Mechanics Lana Sheridan De Anza College Sept 25, 2017

2 Overview of the Course Topics Kinematics. Describing motion of objects without regard to forces. Dynamics. Finding the evolution of a system by considering the forces acting on it.

3 Overview of the Course: Textbook Topics What we will cover Chapters 1-13 of Serway & Jewett, pretty much in order, skipping some things in Chapter 12, and including a few things from Chapter 15. Book Physics for Scientists and Engineers (Vol. 1), 9th Edition, Serway & Jewett Other Books Fundamentals of Physics Extended, Halliday, Resnick, and Walker Feynman Lectures on Physics, Vol 1 Physics for Scientists and Engineers, Knight

4 Overview of the Course: Textbook Topics What we will cover Kinematic motion in 1 & 2 dimensions, parabolic motion, circular motion Vectors, relative motion Forces, Newton s Laws Energy Linear momentum, collisions, rockets Rotation Angular momentum, gyroscopes Statics Simple harmonic motion / oscillations Gravitation and motion of planets

5 Overview of the Course Should I take this course? You should if: You enjoy physics and other technical subjects. You are able to spend time out of class working through ideas on your own. You like solving new problems. You will ask questions when you don t understand something.

6 Overview of the Course Should I take this course? You should if: You enjoy physics and other technical subjects. You are able to spend time out of class working through ideas on your own. You like solving new problems. You will ask questions when you don t understand something. You should not if: You just want to be told what to memorize so you can pass a test. You are not confident with geometry / trigonometry. You do not have at least 12 hours of time outside of class to dedicate to this class.

7 Overview of the Course Make sure you will have enough time to study for this class! From Allot 2 hours of study outside of class for each unit taken. For this class, a minimum of 12 hours a week outside of class.

8 How to do well in physics (or anything) Stephen Curry, on what it takes to succeed: If you take time to realize what your dream is and what you really want in life no matter what it is, whether it s sports or in other fields you have to realize that there is always work to do, and you want to be the hardest working person in whatever you do, and you put yourself in a position to be successful. And you have to have a passion about what you do.

9 How to do well in physics (or anything) Wayne Gretzky, when asked if his apparent genius at making hockey plays was actually the result of countless hours of practice: Absolutely. That s a hundred percent right. It s all practice. I got it from my Dad. Nine out of ten people think it s instinct, and it isn t. Nobody would ever say a doctor had learned his profession by instinct; yet in my own way I ve put in almost as much time studying hockey as a medical student puts in studying medicine.

10 How to do well in physics (or anything) Wayne Gretzky, when asked if his apparent genius at making hockey plays was actually the result of countless hours of practice: Absolutely. That s a hundred percent right. It s all practice. I got it from my Dad. Nine out of ten people think it s instinct, and it isn t. Nobody would ever say a doctor had learned his profession by instinct; yet in my own way I ve put in almost as much time studying hockey as a medical student puts in studying medicine. Genius is one percent inspiration, ninety-nine percent perspiration. Thomas Edison

11 Useful Survival Trick

12 Useful Survival Trick When you get stuck, use a search engine.

13 Other Resources Resources for when you have questions Me. You can me, ask me before class, or come to my office hours. Wed 11:30am-12:30pm; Fri 10:30-11:30am Each other. Work together! It will improve your understanding. The Math & Science Tutorial Center. Where to look for course materials Course Studio. My website on the De Anza Physics page. lanasheridan/

14 Overview of the Course Evaluation Three tests and a final exam. Four collected homework assignments. Quizzes. Labs. Other Assignments Uncollected homework problems from the textbook. (You still need to do them.) Read the textbook.

15 Overview of the Course Evaluation Quizzes (8%) 3 Tests, equally weighted (26%) Final exam (30%) 4 collected HWs (16%) Labs (20%)

16 Overview of the Course Evaluation Projected Grading Scheme: 95% 100% = A+ 88% 94% = A 85% 87% = A 82% 84% = B+ 73% 81% = B 70% 72% = B 67% 69% = C+ 58% 66% = C 46% 57% = D 0% 45% = F

17 Overview of the Course Note about presentation of work For each problem make sure your method is clear. If there is an equation or principle you are using, write it out at the start of your solution. Underline, box, highlight, or unambiguously emphasize the answer. If the reasoning is not clear, the answer is not correct. Give your answers to a reasonable number of significant figures.

18 Overview of the Course Note about presentation of work For each problem make sure your method is clear. If there is an equation or principle you are using, write it out at the start of your solution. Underline, box, highlight, or unambiguously emphasize the answer. If the reasoning is not clear, the answer is not correct. Give your answers to a reasonable number of significant figures. Even correct answers without clear, correct reasoning, will lose most of the possible points.

19 Overview of the Course Note about collected assignments If you cannot come to class on a due date, me the assignment and bring the hard copy to the next class. If you are ill, or will have a problem handing in an assignment on time, come talk to me before the due date.

20 Course Tool Nearpod Allows me to ask multiple choice questions or do surveys, and get real-time feedback. You can remain anonymous. You need a device connected to the internet. Two choices: 1 Install the Nearpod app OR 2 Go to Then: Enter the CODE.

21 Course Survey and Quiz Socket Trial Run 1 Why are you taking this course? A Because physics is awesome. B Because I want to go into a technical field, eg. science, engineering, computer science, etc. C Because knowing more physics will make me better at my current job. D Because I have to be here to get the course credit.

22 Course Survey and Quiz Socket Trial Run 2 Do you have a copy the textbook already? A Yes. B I will get it today. C I will get it this week. D I plan to use the library s copy.

23 Course Survey and Quiz Socket Trial Run 3 Realistically, how much time do you have to work on this course outside of class? A As much time as it takes to learn everything! B hours a week. C hours a week. D 5-10 hours a week. E I won t have time to work on this course outside of class.

24 Course Survey and Quiz Socket Trial Run 4 What was your previous physics course? A Physics 4A or 2A. B Physics 10 or Physics 50. C Honors or similar high school physics. D AP Physics.

25 Course Survey and Quiz Socket Trial Run 5 How comfortable are you with basic calculus? A I know several methods to solve differential equations. B Differentiation and simple integrals are fine. C Differentiation is fine, but I don t know about integration. D I have finished a pre-calculus course, but not a calculus course.

26 What is there to learn in this course? Questions we want to be able to answer: If you stand on a balcony and throw a ball directly upward and another ball directly downward with the same speed, how do their speeds compare just an instant before each hits the ground?

27 What is there to learn in this course? Questions we want to be able to answer: If you stand on a balcony and throw a ball directly upward and another ball directly downward with the same speed, how do their speeds compare just an instant before each hits the ground? Why do you need to slow down when exiting the highway onto a cloverleaf interchange? What force(s) keep your car in the lane as you make the turn?

28 What is there to learn in this course? Questions we want to be able to answer: If you stand on a balcony and throw a ball directly upward and another ball directly downward with the same speed, how do their speeds compare just an instant before each hits the ground? Why do you need to slow down when exiting the highway onto a cloverleaf interchange? What force(s) keep your car in the lane as you make the turn? How does a parachute help slow a skydiver s fall?

29 What is there to learn in this course? Questions we want to be able to answer: If you stand on a balcony and throw a ball directly upward and another ball directly downward with the same speed, how do their speeds compare just an instant before each hits the ground? Why do you need to slow down when exiting the highway onto a cloverleaf interchange? What force(s) keep your car in the lane as you make the turn? How does a parachute help slow a skydiver s fall? Does a smooth solid ball roll down a hill faster than a smooth solid cylindrical battery? If so, then why?

30 What is there to learn in this course? Some questions: Why are door knobs always on the far side of the door from the hinges?

31 What is there to learn in this course? Some questions: Why are door knobs always on the far side of the door from the hinges? How is it that a figure skater can spin quickly enough to make 3 or 4 revolutions in a single jump, but then slow their rotation enough to land smoothly on a skate edge?

32 What is there to learn in this course? Some questions: Why are door knobs always on the far side of the door from the hinges? How is it that a figure skater can spin quickly enough to make 3 or 4 revolutions in a single jump, but then slow their rotation enough to land smoothly on a skate edge? Why is a top or gyroscope able to stand on its tip, even at an angle, when it is spinning, but not when it isn t spinning?

33 What is there to learn in this course? Some questions: Why are door knobs always on the far side of the door from the hinges? How is it that a figure skater can spin quickly enough to make 3 or 4 revolutions in a single jump, but then slow their rotation enough to land smoothly on a skate edge? Why is a top or gyroscope able to stand on its tip, even at an angle, when it is spinning, but not when it isn t spinning? How can a pendulum clock keep accurate time, since friction slows pendulum arm?

34 What is there to learn in this course? Some questions: Why are door knobs always on the far side of the door from the hinges? How is it that a figure skater can spin quickly enough to make 3 or 4 revolutions in a single jump, but then slow their rotation enough to land smoothly on a skate edge? Why is a top or gyroscope able to stand on its tip, even at an angle, when it is spinning, but not when it isn t spinning? How can a pendulum clock keep accurate time, since friction slows pendulum arm? What laws govern the motion of the planets?

35 This Course Goals: be able to answer those types of conceptual questions know how to use theory to solve problems understanding principles and how they apply to technology

36 What is Physics? Physics is the science of fundamental interactions of matter and energy.

37 What is Physics? Physics is the science of fundamental interactions of matter and energy. Physicists (and others who use physics) want to predict accurately how an object or collection of objects will behave when interacting. Why? to better understand the universe to build new kinds of technology (engines, electronics, imaging devices, mass manufacturing, energy sources) to build safer and more efficient infrastructure to go new places and explore to prepare for the future

38 What is Physics? Physics is the science of fundamental interactions of matter and energy. How is it done? Make a simplified model of the system of interest, then apply a principle to make a quantitative prediction.

39 What is Physics? Physics is the science of fundamental interactions of matter and energy. How is it done? Make a simplified model of the system of interest, then apply a principle to make a quantitative prediction. System Any physical object or group of objects about which we would like to make quantitative predictions.

40 What is Physics? Physics is the science of fundamental interactions of matter and energy. How is it done? Make a simplified model of the system of interest, then apply a principle to make a quantitative prediction. System Any physical object or group of objects about which we would like to make quantitative predictions. eg. a pool table. The system might include the balls, the sides of the table, but maybe not the whole Earth. And certainly not the Andromeda galaxy.

41 What is Physics? Model A simplified description of a system and its interactions that includes only what is necessary to make predictions.

42 What is Physics? Model A simplified description of a system and its interactions that includes only what is necessary to make predictions. eg. the billiard balls are made up of atoms, but we can make very accurate predictions about their motion and collisions by just pretending they are uniform rigid spheres.

43 What is Physics? Model A simplified description of a system and its interactions that includes only what is necessary to make predictions. eg. the billiard balls are made up of atoms, but we can make very accurate predictions about their motion and collisions by just pretending they are uniform rigid spheres. Hypothesis An educated guess about a relationship between measurable quantities. It must be falsifiable by observations or experiments.

44 What is Physics? Theory A refined quantitative model for making predictions that has been verified by multiple groups of researchers and is understood to have some regime of validity.

45 What is Physics? Theory A refined quantitative model for making predictions that has been verified by multiple groups of researchers and is understood to have some regime of validity. eg. Newtonian Mechanics - very accurately predicts the motion of billiard balls and the motion of planets, but not the perihelion precession of Mercury, and not the behavior of electrons in atoms.

46 What is Physics? Theory A refined quantitative model for making predictions that has been verified by multiple groups of researchers and is understood to have some regime of validity. eg. Newtonian Mechanics - very accurately predicts the motion of billiard balls and the motion of planets, but not the perihelion precession of Mercury, and not the behavior of electrons in atoms. Valid when v << c, gravitational fields are not too strong, distances are much bigger than l p (Planck length), etc.

47 What is Physics? Law A pattern in nature that can be described very concisely, often in a single mathematical equation.

48 What is Physics? Law A pattern in nature that can be described very concisely, often in a single mathematical equation. eg. F = m a ( If I push this shopping cart twice as hard, it will accelerate twice as fast. )

49 Newtonian Mechanics This course will only cover Newtonian Mechanics. We will look at motion from knowing the acceleration and object experiences. We will analyze forces to consider what acceleration an object will experience. We will also consider the energy of a system to find its motion. There are other ways of doing this analysis: Lagrangian Mechanics and Hamiltonian Mechanics. They are not covered in the course.

50 What Other Physical Theories Do You Know Of??

51 Summary Course overview Physical hypotheses, models, theories, laws Measurements Homework Get the book: Physics for Scientists and Engineers (Vol. 1), 9th Edition, Serway & Jewett Read Chapter 1 and make notes on it.