A "critical mass" is needed for a chain reaction because
A) if the mass is too small the temperature achieved during fission will be too low to sustain the reaction.
B) if the mass is too large, the temperature will get too high and the entire mass will blow up without fissioning.
C) if the mass is too large, the density will be too high to sustain a chain reaction.
D) if the mass is too small, too many neutrons will leak out without causing fission.
E) if the mass is too small, there will not be enough uranium to start the reaction.
D
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What is the apparent path of the Sun against the background of stars?
a. ecliptic b. zenith c. nadir d. elliptic e. shadow
At last, someplace fairly comfortable. Very weak gravity is holding you to the surface of the small object on which you sit. Your object is apparently moving away from a star, perhaps one that it orbits with a period of thousands of years
Around you, geysers are spouting gas into space. Looking back along the object's orbit, you see particles of dust that the geysers apparently blew off the object when it was nearer to the star that it is now leaving behind. You conclude that the geysers were recently much more active but are now settling down into a quiescent state that may last for millennia. You also soon realize that you are closer to home than you have been in all your previous journeys. Perhaps if you can somehow find a small rocket, a heat shield, and a good parachute, you can escape and head home for your final exam. Where are you? A) You are on an asteroid near the center of a galaxy, heading in toward a massive black hole. B) You have been shrunk in size and are riding a grain of interstellar dust that is carrying you on an orbit about our very own Sun. C) You are riding a jet of gas from a quasar that is headed in the direction of an ordinary star. D) You are on comet Hale-Bopp, circa May 1997. E) You are at Disneyland on the Moon, riding the new "wild and wet" roller coaster.
A bowling ball of mass 7.5 kg and diameter 18 cm rolls without slipping down a 10-m bowling lane with a constant speed 4.3 m/s
(a) Through what angle does the bowling ball turn as it travels the length of the lane? (b) What is the angular speed of the bowling ball? (c) Calculate the maximum radial acceleration that a point on the surface of the bowling ball could have. (d) Calculate the tangential acceleration of a point on the surface of the bowling ball.