Scientists do not know what dark energy is, yet they claim that it is the dominant constituent of the mass-energy of the universe. What (if any) evidence supports this claim?
A) There are two lines of evidence: (1) measurements of the accelerating expansion and (2) the universal geometry inferred from the cosmic microwave background.
B) There are two lines of evidence: (1) the fact that the universe is expanding and (2) the observed ratio of deuterium to hydrogen.
C) The only evidence comes from observations of white dwarf supernovae that indicate the expansion rate is accelerating.
D) The claim comes from models of the Big Bang, but it is not backed up by any observational evidence.
A) There are two lines of evidence: (1) measurements of the accelerating expansion and (2) the universal geometry inferred from the cosmic microwave background.
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Consider the potential energy U(x) = (1.0 J/m3)x3 - (8 J/m2)x2 + (15 J/m)x + 8.0 J. Find the turning points of the bound motion when the energy E is 8.0 J
A) 1.0 m and 7.0 m B) 3.0 m and 4.0 m C) 2.0 m and 4.0 m D) 3.0 m and 5.0 m E) 1.44 m and 5.56 m
A particle (mass = 2.0 mg, charge = ?6.0 ?C) moves in the positive direction along the x axis with a velocity of 3.0 km/s. It enters a magnetic field of (
) mT. What is the acceleration of the particle?
A.
? 27
) m/s2B.
+ 27
) m/s2C.
+ 18
) m/s2D.
? 18
) m/s2E.
? 27
) m/s2Calculate the radius in nanometers of the orbit of a hydrogen atom's electron with n = 5
a. 0.27 b. 2.7 c. 1.3 d. 0.13
Which terrestrial world has the most atmosphere?
A) Venus B) Earth C) Mars D) Mercury.