Before light can undergo total internal reflection when incident on material 2 from material 1, what must be true of the indices of refraction?
a. n1 = n2
b. n1 < n2
c. n1 > n2
d. Either n1 or n2 must be equal to 1.
c
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A circular space station (shaped like a big wheel) rotates 100 times in one hour. The apparent weight of an astronaut standing on the inside surface of the outer wall is equal to her weight on earth. How far from the axis of rotation is the inside surface of the station’s outer wall?
A. 322 m B. 102 m C. 56 m D. 1012 m
How can meteorites from the Moon or Mars have made it to Earth?
A) Impacts on those worlds blasted rocks into space that eventually fell to Earth. B) Those worlds spin rapidly enough to have sent some rocks from their surfaces into space. C) The meteorites from the Moon and Mars were never actually part of those worlds; they are just rocks that formed in the same vicinities of the solar system. D) The solar wind gradually blew material off of the surfaces of these worlds, and once in space it collected together to make the meteorites.
The half-life of uranium-232 is 70 years. The time for 3/4 of a sample of uranium-232 to decay is __________
Fill in the blank(s) with correct word
A 30-cm-OD pipe with a surface temperature of 90°C carries steam over a distance of 100 m. The pipe is buried with its center line at a depth of 1 m, the ground surface is –6°C, and the mean thermal conductivity of the soil is 0.7 W/(m K). Calculate the heat loss per day, and the cost of this loss if steam heat is worth $3.00 per 106 kJ. Also, estimate the thickness of 85% magnesia insulation necessary to achieve the same insulation as provided by the soil with a total heat transfer coefficient of 23 W/(m2 K) on the outside of the pipe.
GIVEN
FIND
(a) The heat loss per 24 hour day
(b) The value of the lost heat
(c) The thickness of 85% magnesia insulation necessary to achieve the same insulation
ASSUMPTIONS
Steady state conditions
Uniform thermal conductivity
Two dimensional heat transfer from the pipe
SKETCH
