The Big Bang theory is supported by two major lines of evidence that alternative models have not successfully explained. What are they?
A) (1) the existence and specific characteristics of the observed cosmic microwave background
(2) the observed overall chemical composition of the universe
B) (1) the early universe was hot and dense
(2) we see distant galaxies as they were in the distant past
C) (1) the episode of inflation thought to have occurred in the early universe
(2) the separation of gravity and the other forces at the end of the Planck era
D) (1) the universe is expanding
(2) the observed ratio of spiral to elliptical galaxies in the universe
A) (1) the existence and specific characteristics of the observed cosmic microwave background
(2) the observed overall chemical composition of the universe
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Calculate the heat loss through a 1-m *3-m glass window 7-mm-thick if the inner surface temperature is 20°C and the outer surface temperature is 17°C. Comment on the possible effect of radiation on your answer.
IVEN
• Window: 1 m by 3 m
• Thickness (L) = 7 mm = 0.007 m
• Surface temperature
? Inner (Ti) = 20°C
? outer (To) = 17°C
FIND
• The rate of heat loss through the window (q) ASSUMPTIONS
• One dimensional, steady state conduction through the glass
• Constant thermal conductivity
SKETCH
PROPERTIES AND CONSTANTS
Thermal conductivity of glass (k) = 0.81 W/(m K)
The operation of an electric motor depends on which of the following effects?
a. the Doppler effect b. the photoelectric effect c. the force acting on a current-carrying wire in a magnetic field d. current from the motion of a wire in a magnetic field
Magma that solidifies before reaching Earth's surface is called
A) intrusive igneous rock. B) plutonic rock. C) a pluton. D) all of the above.
Convection is important in stars because it
a. increases the temperature of the star. b. mixes the gases of the star. c. transports energy outward in the star. d. carries the neutrinos to the surface of the star where they can escape. e. b and c