Answers: 3
Physics, 22.06.2019 09:00
Sobre transformações cĂclicas, sĂŁo feitas algumas afirmações, determine quais estĂŁo corretas. i – a variação de energia interna em uma transformação cĂclica Ă© nula; ii – o trabalho, em uma transformação cĂclica, Ă© sempre positivo; iii – ao completar um ciclo, o gás tem a mesma temperatura com a qual começou a transformação; iv – uma transformação cĂclica Ă©, obrigatoriamente, composta de transformações conhecidas, como adiabática, isocĂłrica, etc: a) i e iii b) i e ii c) ii e iii d) i e iv e) iii e iv
Answers: 1
Physics, 23.06.2019 08:00
Athin electrical heater is inserted between a long circular rod and a concentric tube with inner and outer radii of 20 and 40 mm. the rod (a) has a thermal conductivity of ka = 0.15 w/(m*k), while the tube (b) has a thermal conductivity of kb = 0.8 w/(m*k) and its outer surface is subjected to convection with a fluid of temperature t= -15°c and heat transfer coefficient 60 w/(m2 *k). the thermal contact resistance between the cylinder surfaces and the heater is negligible. (a) determine the electrical power per unit length of the cylinders (w/m) that is required to maintain the outer surface of cylinder b at 15°c. (b) what is the temperature at the center of cylinder a?
Answers: 2
18. A child jumps on a trampoline. Which of Newton’s Laws of Motion apply to the scenario pictured a...
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