On a large scale, we find the universe to have voids and ________ structure
Fill in the blank(s) with correct word
filamentary
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An airplane traveling at half the speed of sound emits sound at a frequency of 5 000 Hz. At what frequency does a stationary listener hear the sound as the plane approaches, and after it passes by? Assume the airplane is not flying very high
Dimensional Analysis: The kinetic energy K of an object of mass m moving with speed v is given by the formula K = 
mv2. The SI unit of kinetic energy is the joule, J. Use this formula to express the joule in terms of the fundamental SI quantities of mass, length, and time.
A. J = kg ? m/s B. J = kg ? m/s2 C. J = kg2 ? m2/s2 D. J = kg ? m2/s2
The temperature of a quantity of an ideal gas is
a. one measure of its ability to transfer thermal energy to another body. b. proportional to the average molecular kinetic energy of the molecules. c. proportional to the internal energy of the gas. d. correctly described by all the statements above. e. correctly described only by (a) and (b) above.
A frozen-food company freezes its spinach by first compressing it into large slabs and then exposing the slab of spinach to a low-temperature cooling medium. The large slab of compressed spinach is initially at a uniform temperature of 21°C; it must be reduced to an average temperature over the entire slab of –34°C. The temperature at any part of the slab, however, must never drop below –51°C. The cooling medium which passes across both sides of the slab is at a constant temperature of –90°C. The following data may be used for the spinach: density = 80 kg/m3; thermal conductivity = 0.87 W/(m K); specific heat = 2100 J/(kg K). Present a detailed analysis outlining a method estimate the maximum thickness of the slab of spinach that can be safely cooled in 60 min.
GIVEN
• Large slabs of spinach are exposed to a low-temperature cooling medium
• Initial uniform temperature (To) = 21°C
• Average temperature must be reduced to –34°C
• The temperature at any part must never drop below –51°C
• Cooling medium temperature (T?) = –90°C
• Density of spinach (?) = 80 kg/m3
• Thermal conductivity (k) = 0.87 W/(m K)
• Specific heat (c) = 2100 J/(kg K)
FIND
• Present a detailed analysis outlining a method to estimate the maximum thickness of the slab of spinach that can be safely cooled in 60 min
ASSUMPTIONS
• One dimensional conduction through the slab
• Constant and uniform thermal
properties
• The average temperature within the slab is equal to the average of the center and surface temperatures
SKETCH
