Our Sun is made of about 28% helium (by mass). Where did this helium come from?
A) Fusion in stars
B) The Big Bang only
C) Mostly from fusion in stars with a small contribution from the Big Bang
D) Mostly from the Big Bang with a small contribution from fusion in stars
E) Radioactive decay of heavier elements only
D) Mostly from the Big Bang with a small contribution from fusion in stars
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Very little hydrogen is found in the spectrum of a(n) ________ supernova
Fill in the blank(s) with correct word
The Emergency Core Cooling System is used in the event of an accident to ________
a. stop the fission reactions b. reduce fuel rod temperatures c. provide backup power to control rods d. change the decay heat of the fuel pellets
The electrons in a cloud of hydrogen gas are making the transitionfrom excited states tothe ground state. What does the spectrum of this cloud of gas lookalike?
a) It will be completely black at all wavelengths. b) It will be bright at every wavelength, giving off some radio waves, some visible light,and X-rays. c) It will consist of a few bright emission lines at very specific wavelengths. d) It will be bright at most colors, but with some dark absorption linesat very specific wavelengths. e) It will be identical to the spectrum of the Sun.
A point charge (-5.0 mC) is placed on the x axis at x = 4.0 cm, and a second charge (+5.0 mC) is placed on the x axis at x = -4.0 cm. What is the magnitude of the electric force on a third charge (+2.5 mC) placed on the y axis at y = 3.0 cm?
a. 90 N b. 45 N c. 54 N d. 72 N e. 36 N