Course: Phys-109 General Physics I. Text book: Physics, 6 th edition, D. C. Giancoli.

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1 Few Initial Remarks Course: Phys-109 General Physics I Text book: Physics, 6 th edition, D. C. Giancoli.

2 Few Initial Remarks Instructor: Dr. Mauricio Barbi Tel: Office: LB-212 Website: Office Hours: Monday, W ednesday and Friday, 13:00-14:00h

3 My research interests: Few Initial Remarks I am an Experimental High Energy Particle (HEP) physicist 1- Search for Dark Matter (connection between Particle Physics and Cosmology with implications on the structure of the universe) 2- Study of Neutrino Oscillation phenomena (recently observed). Potential implication in several areas with consequences that might include change in some of the current physics theories.

4 Few Initial Remarks Chapters to be covered: 1. Measurement; Estimating 2. Kinematics in One Dimension 3. Kinematics in Two Dimensions; Vectors 4. Dynamics (Newton s Laws of Motion) 5. Circular Motion; Gravitation 6. Work and Energy 7. Linear Momentum 8. Rotational Motion 9. Static Equilibrium; Elasticity and Fracture 23. Light: Geometric Optics

5 Class Grading Few Initial Remarks 1. Weekly assignments: 25% 2. Midterm Exam: 15% (October 16, 2008) 3. Laboratory: 15% 4. Comprehensive Final Exam: 45% (December 16, 2008) Notes: i. You will not be allow ed to write the final exam if you have failed the laboratory. ii. If you fail the final, your grade will be given 100% of this exam. iii.if, for any well justified reason, you miss the midterm exam, the final exam will account for 60% of your grade. iv.an equation sheet and a list with fundamental constants will be provided for the exams. No other aids will be allowed such as calculators, electronic translators, cell phones, ipods, laptops, etc, without permission.

6 Few Initial Remarks Assignments: Assignments have to be handed in at the beginning of the class on the due date indicated on the class website. Late assignments will be tolerated if handed in no later than the beginning of the next class following the original due date with a cumulative 10% a day penalty to the assignment. Solutions of problems have to be given in full and written clearly, showing all your work and detailing your calculations in an organized way. Ineligible solutions will not be considered.

7 Few Initial Remarks Tutorials: A Tutorial session has been scheduled for every Wednesday between 4:30pm and 5:30pm in CL-127 until the end of the semester. Important: University picture ID is required to write exams Special Needs: Feel free to contact me early in the semester to discuss issues regarding any special needs. You should also contact the Coordinator of Special Needs Services at

8 Few Initial Remarks Last, but not least! I encourage students to ask questi ons in class. Discussions other than physics will not be tolerated. You can also come to my office at my office hours for any physics-related discussion.

9 Chapter 1 Introduction, Measurement, Estimating

10 1. The Nature of Science Units of Chapter 1 2. Physics and Its Relation to Other Fields 3. Models, Theories, and Laws 4. Measurement and Uncertainty; Significant Figures 5. Units, Standards, and the SI System 6. Converting Units 7. Order of Magnitude: Rapid Estimating 8. Dimensions and Dimensional Analysis

11 The Nature of Science Observation: important first step toward scientif ic theory; requires imagination to tell what is important. Theories: created to explain observations; will make predictions. Observations will tell if the prediction is accurate, and the cycle goes on. Models are also very useful during the process of understanding phenomena. It is mostly based on observation and some assumptions that are not necessarily accurate.

12 The Nature of Science How does a new theory get accepted? Predictions agree better w ith data Explains a greater range of phenomena Ptolemy s geocentric view of the universe Copernicus s heliocentric view of the universe

Other fields also use physics, and make contributions to it:

13 Physics and Its Relation to Other Fields Physics is needed in both architecture and engineering. Other fields also use physics, and make contributions to it: physiology, zoology, life sciences, etc. Communication between architects and engineers is essential if disaster is to be avoided.

14 Measurement and Uncertainty; Significant Figures No measurement is exact; there is always some uncertainty due to limited instrument accuracy and difficulty reading results. The photograph to the left illustrates this it would be difficult to measure the width of this 2x4 to better than a millimeter.

15 Measurement and Uncertainty; Significant Figures Estimated uncertainty is written with a ± sign; for example: Percent uncertai nty is the ratio of the uncertainty to the measured value, multiplied by 100:

16 Measurement and Uncertainty; Significant Figures The number of significant figures is the number of reliably known digits in a number. It is usually possible to tell the number of significant figures by the way the number is written: Non-zero digits are always significant; cm has 4 significant figures

17 Measurement and Uncertainty; Significant Figures When are zeroes significant? a) Zeroes placed before other digits are not significant; has two significant figures. b) Zeroes placed between other digits are always significant; 4009 has four significant figures. c) Zeroes placed after other digits but behind a decimal point are significant; 7.90 has three significant figures. d) Zeroes at the end of a number are significant only if they are behind a decimal point as in (c); 7.0 has two significant figures. e) Ambiguity: You can say that the number 8200 has two significant figures, but it could also be three or four. To avoid uncertainty, use scientific notation to place significant zeroes behind a decimal point: x 10 3 has four significant digits 8.20 x 10 3 has three significant digits 8.2 x 10 3 has two significant digits

18 Measurement and Uncertainty; Significant Figures In calculations involving multiplication, division, trigonometric functions, etc, the result has as many significant figures as the number used in the calculation with the fewest significant figures. Example: 11.3 cm x 6.8 cm = 77 cm (two significant figures) and not Problem: How many significant figures do you expect in the following calculation: sin(0.097 x 4.73)? Answer: two significant figures. When adding or subtracting, the number of decimal places (not significant figures) in the answer should be the same as the least number of decimal places in any of the numbers being added or subtracted, or in other words no more accurate than the least accurate number used. Example: 6.1 Kg Kg Kg = 13.5 Kg (and not )

Measurement and Uncertainty; Significant Figures Note: Calculators will not give you the right number of significant figures; they usually give too many but sometimes give too few (especially if

19 Measurement and Uncertainty; Significant Figures Note: Calculators will not give you the right number of significant figures; they usually give too many but sometimes give too few (especially if there are trailing zeroes after a decimal point). The top calculator shows the result of 2.0 / 3.0. The bottom calculator shows the result of 2.5 x 3.2. Remark: When doing multi-step calculations, keep at least one more significant digit in intermediate results than needed in your final answer

20 Units, Standards, and the SI System We will be working in the SI system, where the basic units are meters, kilograms, and seconds (MKS). Other systems: cgs; units are centimeters, grams, and seconds. British engineering system has force instead of mass as one of its basic quantities, which are feet, pounds, and seconds.

21 Units, Standards, and the SI System Quantity Unit Standard Length Meter Length of the path traveled by light in 1/299,792,458 second. Time Second Time required for 9,192,631,770 periods of radiation emitted by cesium atoms Mass Kilogram Platinum cylinder in International Bureau of Weights and Measures, Paris

22 Units, Standards, and the SI System These are the standard SI prefixes for indicating powers of 10. Many are familiar; milli, mega, etc. Y, Z, E, h, da, a, z, and y are rarely used.

23 Dimensions and Dimensional Analysis Dimensions of a quantity are the base units that make it up; they are generally written using square brackets. Example: Speed = distance / time Dimensions of speed: [L/T] Quantities that are being added or subtracted must have the same dimensions. In addition, a quantity calculated as the solution to a problem should have the correct dimensions. Important remarks: - Make sure you always carry units in your calculations; 4 m + 4 m = 8 m (instead of 4 +4 = 8 m). -Always check to see if the units are correct in your results. 5 m/s x 2 s = 10 m

24 Summary of Chapter 1 Theories are created to explain observations, and then tested based on their predictions. A model is like an analogy; it is not intended to be a true picture, but just to provide a familiar way of envisioning a quantity. A theory is much more w ell-developed, and can make testable predictions; a law is a theory that can be explained simply, and which is widely applicable. Dimensional analysis is useful for checking calculations.

25 Summary of Chapter 1 Measurements can never be exact; there is always some uncertainty. It is important to write them, as well as other quantities, with the correct number of significant figures. The most common system of units in the world is the SI system. When converting units, check dimensions to see that the conversion has been done properly. Order-of-magnitude estimates can be very helpful.

Chapter 1 Introduction, Measurement, Estimating

Chapter 1 Introduction, Measurement, Estimating The Nature of Science Units of Chapter 1 Physics and Its Relation to Other Fields Models, Theories, and Laws Measurement and Uncertainty; Significant Figures