mod5 (see also frog 17.1)
energy->Joules (work~amount of water)
power->Watts (how fast the work is done~flow)
EMR: shorter wavelengths more energy e.g. UV, X-rays
KE/PE
PE: chemical bonds, height, spring
KE: motion, freewheel, flowing air/water
temp: KE=1/2mv^2 (macro level)
molecular level:
KE=3/2kT, so T prop to v^2 of molecules
thermodynamics: 3 laws (physics version)
Chemical version:
efficiency; never 100%, 30-60% common
Human 35% eff, diesel engine 60%
energy quality-entropy, disorder, e.g. closet ∆S>0, takes energy input to reduce S (entropy)
open/closed systems: energy, mass
steady state: balance
positive/negative feedback: stable, instable c.g. of ships
n.b.
solar panels: 100 kW = 100kJ per second
wind turbine 2.4 kW = 2.4 kJ per second
stairs: how fast could you run up? Mass?
hot water heater: 4.5 kW for 1 hour = 4.5 kWh
4°C water density greatest: ponds don’t freeze solid in winter
Comments