Physics I Revision PDF

Physics (I) For Robotics and Mechatronics Engineering Students By D\ Afaf Mahmoud Abd-Rabou Associated Professor Physics Department-Faculty of Science – Helwan University Chapter one Units and dimension 1.2 Standards of length, mass, and time How can...

Physics (I) For Robotics and Mechatronics Engineering Students By D\ Afaf Mahmoud Abd-Rabou Associated Professor Physics Department-Faculty of Science – Helwan University Chapter one Units and dimension 1.2 Standards of length, mass, and time How can the physical law be described? Are these physical quantities base or derived? Physical quantities: Standard Physical quantities Derived Physical quantities (Length Mass Time) (Velocity, Acceleration, Density,....) How can the results of physical quantities be reported? What if you know that: Mass of an object is 75 Fankosh A building is 3 glitch tall Three Base Units (SI) Three Base Units (SI)  Example 2 Astronomical distances are sometimes described in terms of light-years (ly). A light-year is the distance that light will travel in one year (yr). How far in meters does light travel in one year. Solution: 1 year = 365.25 days, 1 day = 24 hours, 1 hour = 60 minutes, 1 minute = 60 seconds 1 year =365.25 day *24 hours* 60 min * 60 s =31,557,600 s The distance that light travels in a one year is Systems of units. Units System Length Mass Time CGS Centimeter Gram Second MKS (I.S) Meter Kilogram Second System international (SI) FPS (British) Foot Pound Second 1 Kg = 2.20462 Pound 1 m = 3.28084 Foot 1.4-Dimensional Analysis What is meant by “Dimension” in physics? How it different from unit? Physical Length Mass Time Quantity Dimensio [L] [M] [T] n What are the usage of the dimension? What are the rules ? (1)Check the validity of physical expression. Solution: (2) Deduce a physical equations Example 1: Use dimensional analysis to set up an expression of the form This relationship is correct only if the dimensions of both sides are the same. Solution: No numerical values can be expected  Chapter II Heat and Matter Heat and Matter 1. Introduction. 2. Change of state(phase). 3. Phase diagram. 4. Phase equilibria and phase rule. 5. Effect of pressure on phase transformation. 6. Thermal expansion.  2.1 Introduction.What is Heat? Heat and temp are the same? Dependent variables Cause & (effect) Concept and Nature of Heat. Sensation of Heat Heat Hot Cold Is the size of the matter a factor? When does the flow stop? Concept of Heat Flow of energy (energy in transit) Energy transfers between two systems only due to temp. diff Concept of Temperature. Number related to K.E-units How to represent temperature qualitatively ? Is it macroscopic or microscopic? Is each rise in temperature associated with heat transferer? What is the difference between heat temperature? What Happen when change in temperature take place? (A) Change in state. (B) Change in phase. (C) Change in size. (D) Change in properties What is the difference between state and phase? 2.2 Change of State. 2.2.1 Heating and Cooling Curves. What about the behavior of a substance during heating and cooling? 100 evaporation 80 & condensation 60 4 0 20 0 Melting -20 & solidification  Add Q Add Q Remove Q Remove Q =thermal energy 2.2.3 Phase Diagram. What is the importance of studing phase transformatio and phase diagram? What is the phase diagram? Shows the phases that exist in equilibrium fo a material of given chemical composition. Unary, binary, ternary diagrams What are the types of Phase diagram? (a) H2O (b) CO2 (c) Cu Water Phase diagram P B C S L 1 atom G O A T 1 atom =1.01325 x 105 pascal 0 oC 100 oC ? =76 cm What does different areas, lines, line intersection repre What is the condition of boiling point? Is it constant? Simple phase diagram of one component is divided into two classes: 1st Class: Expand on solidification (water – bismuth) -ve OB slope 2nd Class: Contract on solidification (Co2 – O2) +ve OB slope  Co2 Phase diagram B C B C O O A A Reason of expansion of water during solidification Liquid water molecules Solid water molecules Molecular structure Solid Liquid Gas 2.2.2 Phase Equilibrium and Phase Rule. Gibbs phase rule. ✓ Degree of Freedom(F) Number of independently variable (ways) affecting the range of states in which a system may exist at eq.. ✓Phase(P) Physically distinct portion of a system, separated from other portions by bounding surface. ✓Number of components (C) Minimum number of independent species necessary to define the composition of all phases of the system. Three phase system Ice, water, & vapor Three phase system CaCo3 , CaO & Co2 CaO = CaCo3 - Co2 Phase Rule (Gibbs) How can the degree of freedom increase? Example(1) One phase Example(2) Example(2) What is the meaning that, the degree of freedom of a System is equal to zero?  Numbe Degrees System r of of Comments phases freedom gas, liquid 1 F=1- Bivariant system: lies or solid 1+2=2 anywhere within the area marked G, L or S. gas-liquid, 2 F=1- Univariant system: liquid-solid 2+2=1 lies anywhere along a or line between two gas-solid phases regions (AO, BO or CO). gas-liquid- 3 F=1- Invarient system: can solid 3+2=0 only lie at the triple point (O). 2.2.4 Effect of pressure in Phase Transition. When does a liquid reach the boiling point? ✓ Effect of pressure boiling point. ✓ Effect of pressure on melting or freezing point Contracting on Expanding on solidification solidification Pressure Pressure constrains the process helps the process ✓ What is the effect of pressure on triple point? 2.3 Change in Size: Fundamentals: No Phase transition Change in the average atomic separation Lattice spacing is mean figure Thermal expansion due to asymmetric nature of potential energy 2.3.2 coefficient of thermal expansion. Coefficient: Number measure for property What is the thermal expansion? Is the thermal expansion coefficient +ve or – ve? What are the types of thermal expansion? (A) Linear thermal expansion. (B) Thermal expansion of area. (B) Thermal expansion of volume. 2.3.3 Negative thermal expansion. Anomalous behavior Range of temperature What is the origin negative expansion? (1)Phase transitions, (2)Transverse vibrational modes and (3)Rigid Unit modes. (1)Phase transitions. Liquid water molecules Solid water molecules Molecular structure Water crystallizes into an open hexagonal form. In its liquid state, the molecules are free to roam around wherever they wish. (2)Transverse vibrational modes. Most material expand by heating. Guitar string vibration (3)Rigid Unit modes. coupled rotation of relatively rigid corner sharing SiO4tetrahedra 2.3.4 Change in volume in water. (A) Anomalous behavior. What is the behavior of the volume of water versus T? What about its density from 0 °C to 4 °C? What about its density from 4 °C to 100°C? What about its density & volume at 4 °C? ✓ How do sea animal and plants live? Water freezes from top to down. What is the reason of –ve thermal expansion of water? 2.2.5 Application of Thermal Expansion. (A) Positive Thermal Expansion. ✓ What is the principal? ✓ Automatic control.  Large Small Expansion Expansion Heating is on (B) Negative Thermal Expansion. ✓ What are the problems due to thermal expansion? ✓ Dental fillings Zirconium Tungstate (ZrW2O8) ✓ Optical mirrors ✓ R.I and dimension of fiber optics ✓ Thermal shock ✓ Electronic industry -Circuit board 2.2.6 Thermal stresses. ✓ What is the reason of thermal stresses? ✓ Geometry-external constrains- T gradient Stresses due to expanding constraints. Why F is –ve? When does it be +ve? (B) Thermochromatic Materials. What are the type of materials used? How can the transition temperature change?  PV=const. V/T=const. P/T=const. R = 8.314 J mol–1 K–1 R = 0.0821 Litre atm K–1 mol–1 R = 2 cal K–1 mol–1 1 joule = 0.0099 L atm. 1 joule = 0.2390057361 cal 1 cal = 4.184 kJ = 4184 J. 1 Pascal = ???? N/m2 Volume of one mole STP P=Pa T= 0 C =273 K R=8.31 J/mol.K V =22.4 L (3)Molecular model for pressure of an ideal gas. Kinetic theory or kinetic molecular theory x x y d The root mean square of the molecules speed  For Ideal gas: P v  For real gas: T3 T2 T1 What is the reason of this behavior? What is the effective cross- section for collision ? ✓ How to estimate mean free path? Due to the motion of particles, there is correction as: Heat Heat is thermal energy on move Internal energy: ✓ is the energy that a system has because its T. Work The work done by or on the system is a measure of energy transfer between the system and its Surroundings. (Pi,Vi) (Pf,Vf) (Pf,Vf) (Pi,Vi) Is the work affected by path from initial to final state only? How Heat and work transfer to and from system? (Pi,Vi) (Pf,Vf) What about the difference between Q and W? What the conditions under which Q+? Negative work Positive work Done on the gas Done by the gas 5.3 The First Low of Thermodynamics. What is the first low of thermodynamic? (Pi,Vi) (Pf,Vf) Is U depends on path and process? What about the units of all quantities? Thermodynamics process. (1) Isochoric Process. (i)General law & P-V diagram (ii)Work (iii)What about 1st law ? (vi)Molar heat capacity  (2) Isobaric Process. (i)General law & P-V diagram i f (ii)Work i f (iii)What about 1st law ? (vi)Molar heat capacity Why??  2.4 The Equi-partation of energy. What are the types of motion contributing to the internal energy of a molecule? ✓ Translational ✓ Rotational ✓ Vibrational What are the types of molecules? 2.6 Enthalpy. Total enthalpy Specific enthalpy 2.7 Isothermal Process. (i)General law & P-V diagram (ii)Work (iii)What about 1st law ? (vi)Enthalpy 2.8 Adiabatic Process. No heat enters or leaves the system. (i)General law & P-V diagram (iii)What about 1st law ? What about expansion? What about compression? What is the relation between T & V in adiabatic process?  Application of 2nd law (i) Restriction of first law (ii) Reversible and irreversible process (iii) Limitation efficiency of heat engines. The 2nd law state: The machine completely converting thermal energy into other forms cannot be constructed. 6.2 Heat engines: What is the function of the heat engine? What is the mechanism? What is its feature? During which? (1) Qh from high T source. (2) Work by engine. (3) Qc expelled to low T source. Heat engine. Cyclic: From 1st law: Thermal eff.: When is the efficiency equal one??? Is that possible? automobile engine e=20% diesel engine e=35 : 40 % Impossible “Perfect” heat engine. Kelvin-Plank form It is impossible to construct heat engine that operating in cycle produce no other effect than absorption of thermal energy and the performan of an equal amount work. Refrigerator and heat pump Only by work Little work desired, if no work: perfect ref. Clausius statement It is impossible to construct a cyclical machine th produce no other effect than to transfer heat from one body to another at higher temp. Heat will not flow spontaneously from cold to h 2nd law governs the direction of flow of heat. Only by work as refrigerator. 6.3 Reversible and irreversible proces Is there preferred direction for real process? ✓ Qh Qc What is the feature of the irreversible process What is the feature of the reversible process? In addition to reversible process: Quasi-statically. No dissipative process; heat. No disturb eq.; conduction. Process in nature are irreversible What is the difference between P-V diagra Reversible and irreversible process? 6.4 Carnot Cycle. T = const. T = increase T decrease - T = const. U=0 Carnot Engine. The most efficient engine. heat engine in ideal reversible cycle between 2 reservoirs Carnot Theorem. No real engine operating between two heat reservoirs can be more efficient than a Carno engine. 6.5 The Absolute Temperature Scale. What is the principal at which thermomet Be constructed? What is the absolute temperature of the tr point of water. How can temperature of substance be measured? Absolute zero Temperature of a reservoir at which Carnot Engine will expel no heat. Is it possible? Third Low of thermodynamic "Itis impossible by any procedure to reduce t temperature of any System to zero temperatu in a finite number of finite operations. 6.6 Heat Pump and Heat Refrigerators Heating Mode. Hot reservoir Cold reservoir  Cooling Mode. Cold reservoir Hot reservoir The effectiveness of heat pump. At certain outside T The effectiveness of Refrigerator. An efficient refrigerator? What is the impossible perfect refrigerator? Zeroth Low of thermodynamics. Are T and U state functions? 6.7 Entropy. It is a measure of disorder. How can the behavior of the substance be described? What about the sign of the entropy? How to calculate change in entropy? Does the change of entropy depend on path? Entropy Change For a Reversible cycle What does that mean? Entropy-Temperature diagram. What about the area under the curve? (1) Isochoric process V is constant (2) Isobaric process P is constant (3) Isothermal process T is constant (4) Adiabatic process. T-S diagram of Carnot cycle Entropy change in Carnot heat engine. Ex.2 Quasi-static reversible process for ideal gas. First low Entropy as a function of T & P.. Prove that: Thank You For your Attention