Physics 7A Section C, D Lecturer Dr. Yu Sato Lecture slides available at http://physics7.ucdavis.edu

Course Website http://physics7.ucdavis.edu Click on Physics 7A-C/D

Course Policy Highlights Text College Physics: A Models Approach, Part I by W. Potter  Text  Discussion/Lab Workbook Final Examination March 18, Tuesday, 10:30am –12:30pm Course Grading = Exam grade +/- DL grade.  Exam grade (8 quizzes and the final)  D/L grade Your quiz grade is the average of seven highest individual quiz grades. Your Exam grade is then the higher of either of the two weighting schemes. (a) 50% Quiz grade + 50% Final grade (b) 20%Quiz grade + 80% Final grade

Eight Quizzes during lectures Go to your assigned lecture time Eight Quizzes during lectures Q R S T We need the red circled boxes to identify you The blue circled boxes helps us sort and enter results, getting them back to you faster We categorise/grade your responses based on : (1) your understanding of the problem (2) choice of appropriate model (3) logic to arrive at the (hopefully correct) answer. To find out the meaning of each of the letters, look on the website.

Attendance in the DL(Discussion/Lab) section is MANDATORY Academic Dishonesty Copying during quizzes/exams. Taking a test for another student. Modifying a quiz before asking for a re-grade.

DLs start immediately after lecture. All DLs are in 168 Roessler (i.e. upstairs) First DL starts TODAY IMPORTANT All people who are wait-listed or not enrolled in the DL: Do not join a table or go up to the TA immediately. Collect in a corner, allow the TA to get the lab started and then the TA will address wait-list and enrollment issues.

What is physics? Can ice be colder than 0°C? Why is the sky blue? We begin with the child-like wonder about our everyday world. How does a lightswitch work? How do magnets work? Why does she start spinning so much faster when she pulls her arms and legs in? How do planes fly? What is “rainbow” really?

What does a physicist do? Ouch… Umm why does an apple fall ?? How far does the power of gravity extend?? What does apple’s fall to do with celestial motion? Sir. Isaac Newton

a model is valid and when it is not. Physicists... they observe phenomena and ask questions about them Try to explain phenomena using a few principles (models) - You cannot “pick and choose” when an explanation works - you must have understanding of when a model is valid and when it is not. Physics is taking this approach to explain phenomena in the physical world.

What is physics 7? Models… Discussion/Lab lecture Text Quiz & Final It will require your active participation! (DL grade will reflect this.) Models… Discussion/Lab lecture Text Quiz & Final

What is physics 7? Physics 7 is a 3-quarter series of physics classes, typically taken by bio-science and other non-physical science majors. Physics 7A: Energy conservation, thermodynamics, particle models of matter. Physics 7B: Classical Mechanics, rotational motion, fluids, circuits. Physics 7C: Wave phenomena, optics, electricity and magnetism, the atom and modern quantum mechanics.

Models Useful way to think of and address questions about phenomena (e Models Useful way to think of and address questions about phenomena (e.g. Ideal gas model)

Models in Physics 7A Models can help us organize our thinking, can contain other models, and can be very useful. Models also have limitations: experiment is the final judge. Three-phase model of matter Energy-interaction model Mass-spring oscillator Particle model of matter Particle model of bond energy Particle model of thermal energy Thermodynamics Ideal gas model Statistical model of thermodynamics We start with These two…

Three-Phase model of Matter Example H2O Solid: Keeps its shape without a container Liquid: Takes the shape of the (bottom of) the container. Keeps its volume the same. Gas: Takes the shape and volume of the container.

Three-Phase model of Matter Example H2O Q How do we change the phase of matter? How do we change the temperature of matter? A By adding or removing energy. Often this energy is transferred from, or to the substance as heat Q.

Three-Phase model of Matter Example Melting ice At constant pressure, changes of phase occur at specific temperatures. The phase change temperatures (TMP, TBP) are the same going through the phase change in both directions. The amount of energy added/removed at a phase change (∆HM:Heat of melting, ∆HV:Heat of vaporization) is unique to each substance.

Three-Phase model of Matter Temperature gas l-g coexist TBP s-l coexist liquid TMP solid Energy added or removed

Melting ice Ti= 20°C => Tf = room temperature gas l-g coexist TBP s-l coexist liquid TMP solid Energy of substance

Melting ice Temperature Final gas Initial l-g coexist TBP s-l coexist liquid TMP solid Energy of substance

Energy-Interaction Model Energy systems: There are many different types of energies called energy systems: Emovement (KE) Ethermal Ebond Espring Eelectric Egravity ........ For each energy system, there is an indicator that tells us how that energy system can change. Ethermal: indicator is temperature Ebond: indicator is the initial and final phases

Let’s talk about Conservation of Energy Energy is both a thing (quantity) and a process. You & I contain energy, as do the chairs you sit on and the air we breathe. We cannot see it, but we can measure the transformation of energy (or change, E). Conservation of Energy Energy cannot be created nor destroyed, simply converted from one form to another. If the energy of an object increases, something else must have given that object its energy. If it decreases, it has given its energy to something else. Energy transfer is done through Heat or Work.

Energy Interaction Diagrams Based on the energy interaction model, it shows you how energy is transferred, how energy is conserved between energy systems.

Energy interaction diagrams - closed Ea Eb Ec Conservation of Energy The total energy of a closed physical system must remain constant. In other words, the change of the energies of all energy systems associated with the physical system must sum to zero. Change in system energy = ∆Ea + ∆ Eb + ∆ Ec = 0

Energy interaction diagrams - open Ea Eb Ec Energy added Energy removed Conservation of Energy The change of the energies of all energy systems associated with an open physical system must sum to the net energy added/removed as heat or work. Change in system energy = ∆Ea + ∆ Eb + ∆ Ec = (Energy added) - (Energy removed) = Q+W

Energy interaction diagrams Example Melting ice Ti= 0°C => Tf = room temperature Temperature Final gas Initial l-g coexist TBP s-l coexist liquid TMP solid Energy of substance

Energy interaction diagrams Example Melting ice Process 1 : Ice at T= 0°C => Water at T = 0°C Process 2 : Water at T = 0°C => Water at room temperature Temperature Process1 Final = Process2 initial gas Process1 Initial l-g coexist liquid TMP s-l coexist Process2 Final solid Energy of substance

Energy-Interaction Model Example Melting ice Process 1 : Ice at T= 0°C => Water at T = 0°C Ice Ethermal Ebond ∆T=0 ∆Eth=0 Initial phase Solid, Final phase Liquid

Energy-Interaction Model Example Melting ice Process 1 : Ice at T= 0°C => Water at T = 0°C Ice Heat Ethermal Ebond ∆T=0 ∆Eth=0 Initial phase Solid, Final phase Liquid

Energy-Interaction Model Example Melting ice Process 1 : Ice at T= 0°C => Water at T = 0°C Ice Heat Ethermal Ebond ∆T=0 ∆Eth=0 Initial phase Solid, Final phase Liquid ∆Eth + ∆Ebond= Q+W ∆Ebond= Q

Energy-Interaction Model Example Melting ice Process 2 : Water at T = 0°C => Water at room temperature Ice Ethermal Ebond Initial phase Liquid, Final phase Liquid

Energy-Interaction Model Example Melting ice Process 2 : Water at T = 0°C => Water at room temperature Ice Ethermal Ebond T Initial phase Liquid, Final phase Liquid ∆Ebond= 0

Energy-Interaction Model Example Melting ice Process 2 : Water at T = 0°C => Water at room temperature Ice Heat Ethermal Ebond T Initial phase Liquid, Final phase Liquid ∆Ebond= 0 ∆Eth + ∆Ebond= Q+W ∆Eth= Q

Energy-Interaction Model Example Melting ice Freezing (Ice at T= 0°C <= Water at T = 0°C) Ice Ethermal Ebond ∆T=0 ∆Eth=0 Initial phase Liquid, Final phase Solid

Energy-Interaction Model Example Melting ice Freezing (Ice at T= 0°C <= Water at T = 0°C) Ice Ethermal Ebond Heat ∆T=0 ∆Eth=0 Initial phase Solid, Final phase Liquid

Next lecture Jan 15 Quiz 2 will cover today’s lecture, Discussion/Lab 1 material INCLUDING FNT(For Next Time) questions.