Pyrex glass disks, 4 cm thick and 10 cm diameter at 1800ºC, are cooled in air at 30ºC for 5 minutes. The convective heat transfer coefficient is 10 W/m^2K and the Pyrex density is 2225 kg/m^3, thermal conductivity is 1.4 W/mK, and specific heat is 835 J/kgK. The maximum temperature difference through the pyrex must be less than 200ºC/cm. Determine what this is and make any recommendations.
What will be an ideal response?
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What kind of activity does the surface of Triton experience?
a. nitrogen geysers b. sulfur-based volcanoes c. carbon dioxide geysers d. methane ice tectonics e. liquid nitrogen lava flows
A sandbag motionless in outer space is hit by a three-times-as massive sandbag moving at 12 m/s. They stick together and move at a speed of
A) 3 m/s. B) 4 m/s. C) 6 m/s. D) 8 m/s. E) none of the above
Which of the following is a key factor in explaining why many jovian moons have been more geologically active than the Moon or Mercury?
A) Jovian moons contain much more ice that can melt or deform at lower temperatures than can the rock and metal that make up the Moon and Mercury. B) The jovian moons are considerably larger than the Moon and Mercury and therefore have retained much more internal heat. C) The jovian moons probably have far more internal heat generated by radioactive decay than do the Moon or Mercury. D) Because of their greater distances from the Sun, the jovian moons receive much less heat from the Sun.
Suppose that in a parallel universe, the proton and electron were identical to their counterparts in our own universe EXCEPT that the electron had twice as much charge as our electron. In our present universe,
the radius of the first Bohr orbit for hydrogen is a0 and the speed of an electron in that orbit is v0. In the parallel universe (a) what would be the radius (in terms of a0 ) of the first Bohr orbit for hydrogen? (b) what would be the speed (in terms of v0 ) of an electron in the first Bohr orbit for hydrogen?