T's peggy sue's birthday and she's about to blow out the candles on her cake. brother roger stops the party when he shouts: "look at that! chemical and physical changes taking places on your birthday cake! " how would you respond to roger? a) roger is incorrect. the melting wax is a physical change but there is no chemical change taking place. b) roger is correct. lighting the match is a chemical change and burning the candles is a physical change. c) roger is correct. the melting wax is a physical change and the burning candle wick is a chemical change. d) roger is incorrect. only a chemical change is taking place as evidenced by the light and heat of the burning candles.

Akg a of 55 m at an of 11 ? . if is at 98 km/h,be ?

An internally reversible refrigerator has a modified coefficient of performance accounting for realistic heat transfer processes of where qin is the refrigerator cooling rate, qout is the heat rejection rate, and is the power input. show that copm can be expressed in terms of the reservoir temperatures tc and th, the cold and hot thermal resistances rt,c and rt,h, and qin, as where rtot rt,c rt,h. also, show that the power input may be expressed as 1.39 a household refrigerator operates with cold- and hot-temperature reservoirs of tc 5 c and th 25 c, respectively. when new, the cold and hot side resistances are rc,n 0.05 k/w and rh,n 0.04 k/w, respectively. over time, dust accumulates on the refrigerator’s condenser coil, which is located behind the refrigerator, increasing the hot side resistance to rh,d 0.1 k/w. it is desired to have a refrigerator cooling rate of qin 750 w. using the results of problem 1.38, determine the modified coefficient of performance and the required power input w under (a) clean and (b) dusty coil conditions. internally reversible refrigerator qout qin w high-temperature reservoir low-temperature reservoir th th,i tc,i tc high-temperature side resistance low-temperature side resistance w qin th tc qinrtot tc qinrtot copm tc qinrtot th tc

An initially unpolarized light if intensity 500 w/m^2 passes through four polarizers. the transmission axis between adjacent polarizers is 45∘. what percentage of the initial intensity is transmitted by the system?