which of the following is true for the monuments built by ancient civilization?
A. they are based on stars.
B. they are based on change in the alludes of sun during seasonal changes.
C. the apex of these monuments pointed to stars.
D. the geometry and architecture are based on the heavenly bodies
e. all of the above
e. all of the above
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A 1-m-square copper plate is placed horizontally on 2-m-high legs. The plate has been coated with a material that provides a solar absorptivity of 0.9 and an infrared emissivity of 0.25. If the air temperature is 30°C, determine the equilibrium temperature on an average clear day in which the solar radiation incident on a horizontal surface is 850 W/m2
GIVEN
• A horizontal copper plate in air
• Plate dimensions (s × s) = 1 m × 1 m
• Solar absorptance (?s) = 0.9
• Infrared emittance (?) = 0.25
• Air temperature (T?) = 30°C = 303 K
• Incident solar radiation (qs/A) = 850 W/m2
FIND
• Equilibrium Temperature (Ts)
ASSUMPTIONS
• The sky behaves as a black body at 0 K
• The effect of the legs is negligible
• Air is quiescent
• Radiative heat transfer from the bottom of the plate is negligible
SKETCH
PROPERTIES AND CONSTANTS
The Stephan-Boltzmann constant (?) = 5.67 ? 10–8 W/(m2 K4
The ____ of an object is a measure of the amount of matter it contains. The ____ is a measure of the gravitational force on an object
a. weight; mass b. mass; weight c. energy; force d. force; energy e. momentum; energy
Helium-neon laser light (? = 6.33 × 10^?7 m) is sent through a 0.30-mm-wide single slit. What is the width of the central maximum on a screen 1.0 m from the slit?
a. 2.0 cm b. 4.2 mm c. 1.1 cm d. 2.0 mm e. 0.70 mm
The element uranium (U, atomic no. = 92) often has 146 (or more) neutrons but it will still undergo radioactive decay. Which statement might best describe why?
A) The attractive force of the nucleons has a limited range. B) The isolated neutron is not stable and will undergo spontaneous transformation into a proton and an electron. C) The force is strong with U, but tainted with the dark side it is. D) both A and B E) none of the above