In an open universe, the angles of a triangle add up to
A) more than 180 degrees. B) less than 180 degrees. C) 180 degrees.
B
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The supernova event for a massive star that has lost a large amount of mass to a close binary companion ____
a. does not show hydrogen emission lines in the spectrum of the remnant b. does not produce iron in the core before the explosion c. is less luminous because the companion star absorbs most of the remnant material d. is more likely to produce a neutron star than an isolated supernova e. triggers a supernova in the binary companion
Assume that the inner cylinder in Problem 7.40 is a heat source consisting of an aluminum-clad rod of uranium, 5-cm-OD and 2-m-long. Estimate the heat flux that raises the temperature of the bismuth 40°C and the maximum center and surface temperatures necessary to transfer heat at this rate.
GIVEN
Liquid bismuth flowing through an annulus
Annulus inside diameter (Di) = 5 cm = 0.05 m
Annulus outside diameter (Do) = 6.1 cm = 0.061 m
Bismuth velocity (V) = 4.5 m/s
Bismuth temperature (Tb) = 316°C
Inner cylinder is an aluminum clad uranium heat source
Cylinder length (L) = 2 m
From Problem 7.40: c h
26,800 W/(m2 K)
FIND
(a) The heat flux (QG/At) necessary to raise the bismuth temperature 40°C, and
(b) The maximum center (Tu,o) and surface (Tu,ro) temperatures of the uranium
ASSUMPTIONS
Steady state
The Bismuth temperature given is the bulk Bismuth temperature
Thermal resistance of the aluminum is negligible
Thickness of the aluminum is negligible
SKETCH
A ball is whirled on the end of a string in a horizontal circle at constant speed. Suddenly, the string breaks. Immediately after the string breaks, the ball will
A. have a horizontal velocity that is tangential to the circle. B. have no horizontal velocity. C. have a horizontal velocity toward the center of the circle. D. have a horizontal velocity partly in away from the center of the circle and partly tangent to the circle. E. have a horizontal velocity away from the center of the circle.
Which equation represents the overall nuclear fusion process of the Sun?
a. 4H => 8He + energy b. 2 1H => 1He + energy c. 4 1H => 2 1He – energy d. 4 1H => 4He + energy e. 4 4H => 4He – energy