U.S. industry uses mostly renewable resources for its high economic rate of return
What will be an ideal response?
No, this is not true for all materials. It is truer for some materials than for others.
As Fig. 10 .3 shows, aluminum, copper, lead (in particular), and zinc utilize recycled scrap in
significant amounts.
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A 3-m-long steel rod (k = 43 W/(mK), ? = 1.17 × 10–5 m2/s) is initially at 20°C and insulated completely except for its end faces. One end is suddenly exposed to the flow of combustion gases at 1000°C through a heat transfer coefficient of 250 W/(m2 K) and the other end is held at 20°C. How long does it take for the exposed end to reach 700°C? How much energy will the rod have absorbed if it is circular in cross section and has a diameter of 3 cm?
GIVEN • Steel rod with one end at fixed temperature and the other end exposed to combustion gases FIND (a) Time required for the exposed face to reach 700°C (b) Heat input to the rod
Jupiter and the other jovian planets are sometimes called "gas giants." In what sense is this term misleading?
A) They actually contain relatively little material in a gaseous state. B) The materials they are made of are not the kinds of thing we usually think of as gases. C) They are not in any sense "giants." D) Actually, it's a great description because these worlds are big and gaseous throughout.
Atomic bomb tests demonstrated which aspect of star formation?
A) A shock wave surrounding and compressing a molecular cloud. B) The ignition of fusion that changes a protostar to a star. C) A protostar's movement on the Hayashi track. D) The fragmentation of a molecular cloud. E) A shock wave pushing a molecular cloud from one side.
In the late 1990's, it was announced that the expansion of the Universe is accelerating. What does this imply from the perspective of the big bang?
a. A force exists that we knew nothing about that causes the acceleration. b. The Universe must be closed. c. The Universe is finite. d. The amount of dark matter must be greatly less than the amount of normal matter. e. The Universe must be infinitely old.