Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Theoretical and experimental justification for the Schrödinger equation wikipedia , lookup
Relativistic mechanics wikipedia , lookup
Thermodynamic temperature wikipedia , lookup
Eigenstate thermalization hypothesis wikipedia , lookup
Internal energy wikipedia , lookup
Ch. 5 - Energy I. Energy and Work (p.124-131) Energy and Work Energy Conservation of Energy A. Energy and Work What is energy? Energy is the ability to do work Whenever work is done, energy is transformed or transferred from one system to another When is work done? A. Energy and Work How is energy and work related? work is done only when an object moves. Because the amount of energy transferred is measured by how much work is done – energy and work are expressed in the same unit. But - energy can be present in an object or a system when nothing is happening. However – it can only be observed when it is transferred from one object or system to another. Measured in Joules A. Energy and Work Work transfer of energy through motion force exerted through a distance W = Fd W: F: d: work (J) force (N) distance (m) 1 J = 1 N·m Distance must be in direction of force! B. G Potential Energy Potential Energy (PE) stored energy Cannot be seen depends on position or configuration of an object • Which boulder has greater gravitational PE? • What other ways can an object store energy? B. G Potential Energy Gravitational Potential Energy Depends on mass and height. GPE Mass (m) = kg Free-fall (g) = m/s2 Height (h) = m GPE = mass x free-fall acceleration x height B. G Potential Energy A 65 kg rock climber ascends a cliff. What is the climber’s gravitational potential energy at a point 35 m above the base of the cliff? B. G Potential Energy Type of Potential Energy Gravitational Potential Energy Energy stored due to position above Earth’s surface). Example (objects that are Chemical Energy Energy stored in chemical bonds such as food or fuel. Elastic Energy energy stored by something that can stretch or compress such as a rubber band or spring. Energy stored in chemical bonds such as food or fuel. C. Kinetic Energy Kinetic Energy (KE) energy in the form of motion depends on mass and velocity • Which has the most KE? 80 km/h truck • Which has the least KE? 50 km/h motorcycle 80 km/h 50 km/h 80 km/h C. Kinetic Energy Kinetic energy depends more on speed than on mass. KE = ½ m v mass (m) = kg velocity (v) = m/s C. Kinetic Energy What is the kinetic energy of a 44kg cheetah running at 31 m/s? KE = 22 x 961 2 D. Other Forms of Energy THERMAL The ability to cause change. internal motion of particles MECHANICAL NUCLEAR ENERGY motion of objects changes in the nucleus ELECTRICAL CHEMICAL bonding of atoms joules (J) motion of electric charges D. Other Forms of Energy Mechanical Energy the energy associated with the motion or position of an object. The sum of potential and kinetic energy in a system (Usually involves movement of an object) Chemical Energy is the energy stored in chemical bonds – when the bonds are broken, the released energy can do work. D. Other Forms of Energy Nuclear Energy: energy stored in atomic nuclei – nuclear fission releases energy by splitting nuclei apart, nuclear fusion releases energy by combining 2 nuclei into a larger nuclei. Electromagnetic Energy: a form of energy that travels through space in the form of waves. Visible light and X-rays are examples. D. Other Forms of Energy Electrical energy: results from the flow of charged particles or electrons. Electric charges can exert forces that do work Thermal Energy: energy given off as heat (friction). The total potential and kinetic energy of all the microscopic particles in an object. F. Conservation of Energy How is energy conserved in a closed system? The process of changing energy from one form to another. F. Conservation of Energy Law of Conservation of Energy Energy may change forms, but it cannot be created or destroyed under ordinary conditions. EX: PE KE mechanical thermal chemical thermal Energy Transfer Conservation of Energy Roller Coaster Physics Ch. 5 - Energy II. Thermal Energy Temperature Thermal Energy Heat Transfer A. Temperature Thermal Energy energy given off as heat (friction). The total potential and kinetic energy of all the microscopic particles in an object. A. Temperature Temperature measure of the average KE of the particles in a sample of matter B. Thermal Energy Thermal Energy the total energy of the particles in a material KE - movement of particles PE - forces within or between particles due to position depends on temperature, mass, and type of substance B. Thermal Energy Which beaker of water has more thermal energy? B - same temperature, more mass 80ºC A 80ºC B 200 mL 400 mL C. Heat Transfer Heat thermal energy that flows from a warmer material to a cooler material Like work, heat is... measured in joules (J) a transfer of energy C. Heat Transfer What are 3 types of heat transfer? Conduction Convection Radiation D. Conduction Transfer of heat as a result of direct contact Conduction in gases is slower than in liquids and solids because the particles in a gas collide less often E. Convection Transfer of thermal energy when particles of a fluid move from one place to another Convection currents are important in many natural cycles, such as ocean currents, weather, systems, and movement of hot rock in Earth’s interior F. Radiation Transfer of energy by waves moving through space. All objects radiate energy As an object’s temperature increases, the rate at which it radiates energy increases Summary Quiz C. Heat Transfer Why does A feel hot and B feel cold? Heat flows from A to your hand = hot. Heat flows from your hand to B = cold. 80ºC A 10ºC B C. Heat Transfer Specific Heat (Cp) amount of energy required to raise the temp. of 1 kg of material by 1 degree Kelvin units: J/(kg·K) or J/(kg·°C) Specific Heat Values (J/(kg·K)) Water 4184 Alcohol 2450 Aluminum 920 Carbon (graphite) 710 Sand 664 Iron 450 Copper 380 Silver 235