We know that there are large gaps in the average distances of asteroids from the Sun (within the asteroid belt) because we
A) see the gaps through telescopes.
B) see the gaps via stellar occultation.
C) know they are there theoretically, although we haven't detected them.
D) actually don't know whether there really are gaps or not.
E) have plotted distributions of the orbital radii of the asteroids.
E
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Ball bearings are to be hardened by quenching them in a water bath at a temperature of 37°C. You are asked to devise a continuous process in which the balls roll from a soaking oven at a uniform temperature of 870°C into the water, where they are carried away by a rubber conveyer belt. The rubber conveyor belt, however, is not satisfactory if the surface temperature of the balls leaving the water is above 90°C. If the surface coefficient of heat transfer between the balls and the water may be assumed to be equal to 590 W/(m2 K), (a) find an approximate relation giving the minimum allowable cooling time in the water as a function of the ball radius for balls up to 1.0-cm in diameter, (b) calculate the cooling time, in seconds, required for a ball having a 2.5- cm-diameter, and (c)
calculate the total amount of heat in watts which has to be removed from the water bath in order to maintain a uniform temperature if 100,000 balls of 2.5-cm-diameter are to be quenched per hour.
GIVEN
FIND
(a) An approximate relation giving the minimum allowable cooling time in the water as a function of the ball
radius for balls upto 1.0 cm in diameter
(b) The cooling time, in seconds, required for a ball having a 2.5-cm-diameter
(c) The total amount of heat in watts which would have to be removed from the water bath in order to
maintain its temperature uniform if 100,000 balls of 2.5 cm diameter are to be quenched per hour
ASSUMPTIONS
The ball bearings are 1% carbon steel
SKETCH
High-mass stars evolve differently than medium-mass stars because they are able to fuse _______________
Fill in the blank(s) with correct word
A child has a temperature of 101°F. If her total cross-sectional area is 2 m2, find the energy lost each second (in W) due to radiation, assuming the emissivity is 1 . (Assume the room temperature is 70°F.)
a. 217 b. 180 c. 90 d. 68 e. 850
What are the differing ages and shapes of the 3 main components?
A: young round bulge, old football disk, young elliptical halo B: young bar-like bulge, young plate disk, old spherical halo C: old round bulge, young frisbee disk, young elliptical halo D: old bar-like bulge, young pancake disk, old spherical halo E: old bar-like bulge, old CD disk, young spherical halo