Why is the air over an open flame always moist?
A) The hot flame vaporizes the water in the air above the flame.
B) One of the products of combustion is water vapor.
C) Warm air contains more humidity than cold air.
D) None of the above is true.
Answer: B
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An electric heating blanket is subjected to an acceptance test. It is to dissipate 400 W on the high setting when hanging in air at 20°C. (a) If the blanket is 1.3-m-wide: what is the length required if its average temperature at the high setting is to be 40°C, (b) If the average temperature at the low setting is to be 30°C, what rate of dissipation is possible?
GIVEN
• An electric blanket hanging in air
• Heat dissipation rate (qh) = 400 W
• Air temperature (T?) = 20°C
• Blanket width (w) = 1.3 m
• Average temperatures ? High (Tsh) = 40°C
? Low (Ts1) = 30°C
FIND
(a) The length of the blanket (L) (b) Heat dissipation rate on the low setting (q1) ASSUMPTIONS
• Air is still
• Moisture in the air has a negligible effect
• Blanket is hung vertically with its 1.3 m sides vertical
SKETCH
PROPERTIES AND CONSTANTS
for dry air at the mean temperatures for the two settings
Buoyancy: A piece of aluminum with a mass of 1.0 kg and density of 2700 kg/m3 is suspended from a light cord and then completely immersed in a container of water having density 1000 kg/m3.(a) Determine the volume of the piece of aluminum.(b) Determine the tension in the cord when the aluminum is immersed in the container of water.
What will be an ideal response?
Armor asteroids cross into the orbit of which planet?
a. Mercury b. Venus c. Earth d. Mars e. Jupiter
While the photosphere produces chiefly visible light, most coronal energy is in the form of
A) infrared radiation. B) ultraviolet light. C) X-rays. D) gamma rays. E) radio waves.