1. AP PHYSICS

2. Tuesday, 1/13/09AP PHYSICS “We teach people how to treat us.” Cesar Millan The Dog Whisperer (*rev and rev hw 43 note: water’s high C p 355 and things it causes*)

3. Tuesday, 1/13/09AP Physics The last of Ch. 11 The three ways to transfer heat: conduction – convection – radiation – direct contact with an object having higher temperature (*emphasize direction of flow*) movement of a heated fluid (gas or liquid) electromagnetic waves (infrared) ex. camp fire conduction – convection – radiation – grab the burning wood put hands over the fire (hot air rises) sit beside the fire (radiated heat only)

4. Heat transfer rate (heat current) (*for conduction*) H ≡ Q/Δt units: J/s = W H = Q/Δt  A(T 2 – T 1 )/L H = Q/Δt = kA(T 2 – T 1 )/L k – constant, p. 367 “thermal conductivity” A – cross-sectional area T 2 – higher temperature T 1 – lower temperature L – length (or thickness of slab) (*ice demo*)

5. p. 382 #38 A glass windowpane in a home is 0.62cm thick and has dimensions of 1.0m x 2.0m. On a certain day, the indoor temperature is 25°C and the outdoor temperature is 0°C. (a) What is the rate at which energy is transferred by heat through the glass? (b) How much energy is lost through the window in one day, assuming the temperature inside and outside remain constant. (*multiple layers*)

6. Ch. 12 The Laws of Thermodynamics defn. Internal energy (U) – Most books also call this “thermal” energy. Note: Your book differentiates between them. It calls thermal energy, the part of internal energy that changes when the temperature changes. When we talk about the state of a system we’ll talk about pressure, volume, temperature, and internal energy. For simple systems, the pressure and volume will be the most important information. all of the energy belonging to all the molecules of a system while it is stationary.

7. Here is a very simple system: A gas expanding at constant pressure. W = FΔy (work done BY the gas) = (PA)Δy= PΔV P W = PΔV

8. PV graphs are used to study these systems. The work done BY the system equals the area under the PV curve! NOTE: We can and will have work done ON the system! (*backwards*) (*calculus – W = ∫ P dV*)

9. The work done by a gas from an initial state to a final state depends on the path taken. 12 3 W 2 > W 3 > W 1 HW 44: ws. Ch. 11 problems 30, 33-35 Ch. 12 problems 2 - 6

10. hw 44 30) a) 223W b) 0.0132W c) 0.053W 33) 37X more 35) 0.0899m 3) 11,300J 5) a) 810J b) 507J c) 203J