O vídeo a seguir apresenta uma propriedade interessantíssima do gás hélio: a superfluidez. O hélio é um gás com temperatura de liquefação muito baixa (próximo a 4,2 K) e não pode ser solidificado com pressões maiores do que 25 atm. Entretanto, em condições específicas, como a do vídeo abaixo, o gás hélio pode se liquefazer e gerar esse fenômeno interessante, em que o líquido "sobe" as paredes do recipiente, contrariando a atração gravitacional. A superfluidez, como chamamos, ocorre em temperaturas abaixo de 2,5 K. Calcule o valor equivalente na escala Celsius para a temperatura em que o estado de superfluidez ocorre.

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

Aman throws a football straight into the air. as it rises, it slows down. which type of energy is the football gaining?

If the work required to stretch a spring 3 ft beyond its natural length is 15 ft-lb, how much work is needed to stretch it 27 in. beyond its natural length?