Lectures_2

# Lectures_2 - Energy EATS 1011 0.3 Winter Energy Energy...

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06/06/10 EATS 1011 0.3 Winter Energy

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06/06/10 EATS 1011 0.3 Winter Energy Energy ability or capacity to do work comes in many forms, kinetic , potential , heat etc Energy is conserved = 1st law of thermodynamics. Work is done on matter if it is pushed, pulled or lifted over some distance. e.g. Lifting implies exerting a force against gravity. By doing work on something we give it energy, which can be used to do work on something else. e.g. pulling spring gives stored potential energy The energy stored in an object (internal energy) determines how much work it can do. This is called gravitational potential energy or potential energy potential to do work.
06/06/10 EATS 1011 0.3 Winter Energy ctd e.g. potential energy lifting a mass through a height PE = mgh where: m = mass (kg) g = gravitational acceleration (m/s 2 ) h = distance lifted (m) Units of energy: 1 erg = 1 dyne/cm = 2.388 x 10 -8 cal 1 Joule (J) = 1 Newton meter (N.m) = 0.239cal = 10 7 erg 1 calorie (cal)= 4.186 J = 4.186 x 10 7 erg

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06/06/10 EATS 1011 0.3 Winter Energy ctd Chemical potential energy A substance has potential energy if it can do work when a chemical change can occur (coal, natural gas, chemicals, food have PE) kinetic energy (KE) = Energy of motion KE = 1/2 mv 2 where: m = mass (kg) v = velocity (m/s) Faster moving higher KE. E.g. strong wind has more KE. Kinetic energy of random motion is often referred to as Heat Energy. Energy can’t be destroyed or created, it only moves from one form to another.
06/06/10 EATS 1011 0.3 Winter Atmospheric Heating

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06/06/10 EATS 1011 0.3 Winter Heating Conduction Molecular motions Near surface Thermosphere Convection Macroscopic motions, i.e. winds, turbulence Horizontal, vertical Latent Heat Condensation/evaporation Freezing/fusion/melting sublimation Radiation At the speed of light
06/06/10 EATS 1011 0.3 Winter Fig. 2-5, p.29 The flow of heat is driven by the temperature gradient From hot to cold [-dT/dx] Conduction

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06/06/10 EATS 1011 0.3 Winter Fig. 2-6, p.30 Convection – mass motion - transport
06/06/10 EATS 1011 0.3 Winter Fig. 2-3, p.28 Latent heating/cooling vapour ice 2.5x10 6 J/kg 0.83x10 6 J/kg

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06/06/10 EATS 1011 0.3 Winter Fig. 2-4, p.29 Condensation of water vapour to form water droplets, perhaps rain, heats the atmosphere by latent heat release
06/06/10 EATS 1011 0.3 Winter Electromagnetic Radiation

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06/06/10 EATS 1011 0.3 Winter EMR/light has both wave and particle properties (photon) 2200 λ - wavelength (m) 2200 ν - frequency (s -1 ) C = λν = 3x10 8 m/s speed of light E = h ν (J) h = 6.626x10 -34 J.s
06/06/10 EATS 1011 0.3 Winter Fig. 2-7, p.32

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06/06/10 EATS 1011 0.3 Winter EM radiation ctd “Black Body or Planck Body” is a hypothetical body that emits radiation in a manner so that the total amount of energy is only a function of temperature and the spectral shape is a universal function with a single
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Lectures_2 - Energy EATS 1011 0.3 Winter Energy Energy...

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