Contrast the two types of radio galaxies in structure
What will be an ideal response?
Core-dominated have most of the energy coming from the core, and fading in radio intensity outward in the halo. Lobe structure is related to two jets streaming from the active core, and the radio emissions come mostly from dual lobes of hot gas that stretch out over a million light-years above and below the disk of the galaxy.
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Based on our current theory of Earth's formation, the water we drink likely comes from
A) ice that condensed in the solar nebula in the region where Earth formed. B) chemical reactions that occurred in Earth's crust after Earth formed. C) chemical reactions that occurred in Earth's core after Earth formed. D) material left behind during the giant impact that formed the Moon. E) water-bearing planetesimals that formed beyond the frost line and then impacted Earth.
Planet Z-34 has a mass equal to one-third that of Earth and a radius equal to one-third that of Earth. With g representing, as usual, the free-fall acceleration at the surface of Earth, the free-fall acceleration at the surface of Z-34 is
A) g/3. B) 3g. C) 6g. D) g/9. E) 9g.
The addition of aluminum fins has been suggested to increase the rate of heat dissipation from one side of an electronic device 1-m-wide and 1-m-tall. The fins are to be rectangular in cross section, 2.5-cm-long and 0.25-cm-thick. There are to be 100 fins per meter. The convective heat transfer coefficient, both for the wall and the fins, is estimated at 35 W/(m2 K). With this information, determine the per cent increase in the rate of heat transfer of the finned wall compared to the bare wall.
GIVEN
Aluminum fins with a rectangular cross section
Dimensions: 2.5-cm-long and 0.25-mm-thick
Number of fins per meter = 100
FIND
The per cent increase in the rate of heat transfer of the finned wall compared to the bare wall
ASSUMPTIONS
Steady state heat transfer
SKETCH
If a system undergoes a reversible process,
A) it must be possible to restore the system to its original state. B) it must be possible to restore the surroundings to their original state. C) it must be possible to restore both the system and the surroundings to their original states. D) it is impossible to restore either the the system or the surroundings to their original states. E) the system must not interact with its surroundings.