Give a brief account of the abundance of chemical elements in the Universe

What will be an ideal response?


More massive atoms, such as gold atoms, are made only by short-lived nuclear reactions that occur during a supernova explosion. This explains why lower-mass atoms such as carbon, nitrogen, and oxygen are more common and why more massive atoms-such as gold, silver, platinum, and uranium-are so rare and, often, valuable.Most of the matter in stars is hydrogen and helium. Other elements, including carbon, nitrogen, oxygen, and the rest of what astronomers call metals, were cooked up inside stars. When the galaxy first formed, there should have been no metals because stars had not yet manufactured any. Judging from the composition of stars in the oldest clusters, the gas from which the galaxy originally condensed must have contained about 90 percent hydrogen atoms and 10 percent helium atoms.

Physics & Space Science

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The emissivity of an ideal reflector has which of the following values?

a. 0 b. 1 c. 100 d. infinity

Physics & Space Science

A plastic hose stuffed more or less densely with steel wool and a source of water can act as a model for resistance and electric current in wires. Suppose two one-meter lengths of such a hose were stuffed identically with steel wool

Discuss how one could use this model to determine which of the following would have greater resistance: one length; two lengths connected one after another; two lengths connected side by side, both connected to one source of water. Speculate on the answers as best you are able.

Physics & Space Science

Using graphical methods, estimate the temperatue distribution and the heat transfer per meter depth between the two surfaces at the corner shown in Figure 2-60.

Physics & Space Science

The axis of a long hollow metallic cylinder (inner radius = 1.0 cm, outer radius = 2.0 cm) coincides with a long wire. The wire has a linear charge density of ?8.0 pC/m, and the cylinder has a net charge per unit length of ?4.0 pC/m. Determine the magnitude of the electric field 3.0 cm from the axis.

A. 5.4 N/C B. 7.2 N/C C. 4.3 N/C D. 3.6 N/C E. 2.4 N/C

Physics & Space Science