A picture window in a house is 3 feet high by 5 feet long. If the window is 50ºF and the outside air temperature is -10ºF, estimate the heat transfer by natural convection from the window.
What will be an ideal response?
Treating the window as a vertical flat surface, we need to determine the Grshof number and the Grashof/Prandtl product, called the Rayleigh number, Ra. The characteristic length is 3 feet, the temperature difference is 60ºF = 60ºR, and the Prandtl number is about 0.7. For, which we assume is an ideal gas
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Why are X-rays and gamma rays considered dangerous forms of light? a. These forms of light are only produced by large, dangerous machines. b. There is no form of protection from these forms of light
c. These forms of light break through Earth's atmosphere. d. Photons of these wavelengths have high energy. e. These forms of light cause sunburn.
Energy used for production of ethanol from corn is _____than the energy output
a. more b. less c. the same
A photon whose energy is 8.00 × 10^-15 J is scattered off an electron at a 90° angle. What is the wavelength of the scattered wave?
a. 2.73 × 10^-11 m b. 2.25 × 10^-11 m c. 2.50 × 10^-11 m d. 2.40 × 10^-12 m e. 2.48 × 10^-11 m
What is hydrostatic equilibrium and how is it used to explain the internal stability of a star?
What will be an ideal response?