Why didn't the Big Bang produce many heavier elements than helium?
What will be an ideal response?
By the time helium nuclei could exist in large numbers without being destroyed by the intense radiation field, the universe was about a minute old and the temperature and density were rapidly decreasing. Nuclear fusion reactions to produce heavier elements were possible, but the combination of two helium nuclei or a hydrogen nucleus and helium nucleus produces unstable nuclei. The combination of three helium nuclei produce carbon, but by this time the density of the universe was too low for many three-body collisions to occur. Thus the production of heavier elements had to wait until stellar nucleosynthesis.
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______________are mixtures of metal elements with other elements.
Fill in the blank(s) with the appropriate word(s).
Which of the following is evidence that solar activity affects Earth's climate?
A. The dust bowl of the 1930s in the United States coincided with the complete disappearance of sunspots during that time. B. The Maunder Minimum-a period of abnormally low sunspot numbers-coincided with abnormally cold northern winters. C. The Schwab Cycle-a period of abnormally numerous and large sunspots-preceded a 250-year drought in Africa. D. All of these choices are correct.
If a point charge is located at the center of a cylinder and the electric flux leaving one end of the cylinder is 20% of the total flux leaving the cylinder, what portion of the flux leaves the curved surface of the cylinder?
A) 20% B) 100% C) 80% D) 40% E) 60%
A track star in the broad jump goes into the jump at 10 m/s and launches himself at 20° above the horizontal. How long is he in the air before returning to Earth? Note: g = 9.8 m/s2
a. 0.35 s c. 0.70 s b. 0.42 s d. 0.89 s