What is the most accurate way to determine the distance to a very distant irregular galaxy?
A) using Cepheid variables
B) using a white-dwarf supernova as a standard candle
C) main sequence fitting
D) Hubble's law
B
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The coefficients of static and kinetic friction between a 3.0-kg box and a horizontal desktop are 0.40 and 0.30, respectively. What is the force of friction on the box when a 15-N horizontal push is applied to the box?
A) 4.5 N B) 6.0 N C) 15 N D) 8.8 N E) 12 N
Resolution: What is the minimum distance between two points on the Moon that could be just resolved by the Keck telescope in Hawaii using a wavelength of 600 nm and having perfect optics? The diameter of this telescope mirror system is 10 m, and the distance to the Moon is 380,000 km.
Fill in the blank(s) with the appropriate word(s).
What are the circumstances under which convection can occur in a substance?
A) when the substance is subjected to a strong magnetic field B) when the substance is strongly cooled from underneath C) when dense material is being added to the substance D) when the substance is strongly shaken or disturbed by a strong wind E) when the substance is strongly heated from underneath
If the kinetic energy of a proton is 80% of its total energy, what is the speed of the proton?
A) 0.02c B) 1.0c C) 0.87c D) 0.98c