What is the distinguishing characteristic of what we call ordinary matter (such as the matter that makes up stars, planets, and people)?
A) It is made of subatomic particles that scientists call WIMPs.
B) It emits a great deal of light.
C) It consists of atoms or ions with nuclei made from protons and neutrons.
D) It can attract other matter through the force of gravity.
C
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Why does the Cepheid "standard candle" have limited usefulness beyond 100 Mpc?
A) Distant galaxies are seen in the past, when Cepheid variables behaved differently than they do today. B) Distant galaxies are so young they do not contain Cepheids. C) Cepheids are too faint to be seen beyond that distance, even with HST. D) The light variability of Cepheids diminishes with distance so they do not appear to vary there. E) Older distant Cepheids are of population II, where the period-luminosity relation no longer works.
When you lift a heavy 5.0 kg crate straight up from ground level to a height of 2.0 m above ground level, then you have changed the crate's gravitational potential energy by
A. 98 N. B. an undetermined amount, because it depends on how fast you lifted it. C. 98 m2/s2. D. 98 J. E. 98 kg m/s.
In the nuclear fusion of four hydrogen nuclei to form a helium nucleus, the resultant helium nucleus
A) is more massive than the four hydrogen nuclei, the missing mass being converted into energy B) is radioactive, generating energy by ejected electrons from beta decay C) is less massive than the four hydrogen nuclei, the missing mass being converted into energy D) has exactly the same mass as the four hydrogen nuclei, the energy being generated by the helium nucleus rearranging itself by emitting a gamma ray
Because the _______________ of the Moon and the Sun vary slightly, the disk of the Moon is sometimes too small to cover the disk of the Sun
Fill in the blank(s) with correct word