A horizontally-projected beam of electrons travelling at 55 km/s travels between two parallel plates separated by 7.4 cm, and 12 cm long, between which there is an electric field of 7.2 mV/m upward. If the beam enters the region at a height of 3.7 cm above the lower plate, at what height above the lower plate is the beam when it exits? The electron mass is 
A. 0.9 cm
B. 2.3 cm
C. 5.1 cm
D. 4.6 cm
B. 2.3 cm
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Which one of the phrases below is the current explanation of why the surface of Venus is so hot?
a. Venus's poor reflectivity b. the action of the greenhouse effect caused by carbon dioxide c. always keeping the same face turned toward the Sun d. the action of the greenhouse effect caused by hydrogen
Of these, which is evidence that Mars once had running water on its surface?
A. There are vast amounts of H2O present in Martian rocks. B. Spacecraft have observed channels and dry riverbeds on the Martian surface. C. There is a medium-sized ocean in the Southern Hemisphere of Mars. D. There is no such evidence.
Listed following are several objects in the solar system. Rank these objects from left to right based on their orbital period around the Sun from shortest to longest.
When a gas expands adiabatically,
A) the internal energy of the gas decreases. B) the internal energy of the gas increases. C) there is no work done by the gas. D) work is done on the gas. E) heat flows out of the system.