Which of the following types of electromagnetic radiation has the greatest energy?
a. x-rays
b. visible light
c. radio
d. gamma-rays
e. infrared radiation
D
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The strong force is mediated by
a. the gluon. b. the W– boson. c. the W+ boson. d. All of these choices.
Duff states that equal masses of all substances have equal changes in internal energy when they have equal changes in temperature. Javan states that the change in internal energy is equal to a constant times the change in temperature for every DT, no matter how large or how small DT is, but that the constant is different for different substances. Which one, if either, is correct?
a. Neither, because the specific heat depends on the substance and may vary with temperature. b. Neither, because a change of state may involve release or absorption of latent heat. c. Neither because a substance may do work during a temperature change. d. All of the statements above are correct. e. Only statements (a) and (b) are correct.
If the total resistance between the steam and the air (including the pipe wall and scale on the steam side) in Problem 7.36 is 0.05 m2 K/W, calculate the temperature difference between the outer surface of the inner pipe and the air. Show the thermal circuit.
GIVEN
Atmospheric flow through an annulus with steam condensing in inner tube
Diameters Inside
(Di) = 25 cm = 0.25 m
Outside (Do) = 38 cm = 0.38 m
Steam temperature (Ts) = 149°C
Air velocity (V) = 6 m/s
Total resistance between the steam and air (At Rtot) = 0.05 (m2 K)/W
Air bulk temperature (Tb) = 38°C
From Problem 7.36 heat transfer coefficient on the outer surface of the inner pipe (c h) = 25.4 W/(m2 K)
FIND
The temperature difference between the outer surface of the inner pipe and the air (?T)
ASSUMPTIONS
Steady state
Steam temperature is constant and uniform
Heat transfer to the outer surface is negligible
Air temperature given is the average air temperature
Thermal resistance of inner tube wall and condensing steam is negligible (Inner tube wall surface
temperature = Ts)
SKETCH
A rock falls from a vertical cliff that is 4.0 m tall. At what speed will the gravitational potential energy of the rock-Earth system (relative to the base of the cliff) be equal to its kinetic energy? Assume that air has no effect on the motion of
the rock. A) 3.1 m/s B) 4.4 m/s C) 6.3 m/s D) 8.9 m/s E) 13 m/s