What was the significance of the end of the era of nucleosynthesis, when the universe was about 5 minutes old?
A) It marks the time at which the expansion of the universe had settled down to its current rate.
B) The basic chemical composition of the universe had been determined.
C) It marks the time at which the first stars formed.
D) The proportions of dark matter and luminous matter had been determined.
B
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Which of the following is not key evidence in support of the idea that all life today shares a common ancestor?
A) We have identified fossils of the first life forms that ever existed on Earth. B) All life uses DNA and the same genetic code. C) Mapping of gene sequences shows how life is all related. D) All life builds proteins from the same amino acids and uses ATP to store energy in cells.
Process of Science: The idea of quantum tunneling seems very counterintuitive. However, there is considerable evidence to support it. Describe one such line of evidence
What will be an ideal response?
A factory siren indicating the end of a shift has a frequency of 80 Hz. What frequency is perceived by the occupant of a car traveling towards the factory at 30 m/s? The speed of sound in air is 343 m/s
A) 83 Hz B) 85 Hz C) 87 Hz D) 89 Hz E) 91 Hz
A 20-N horizontal force pushes an object along a rough floor so that the object moves with a constant velocity of 6.0 m/s. How much power does this force deliver to the object?
A) 5.0 W B) 20 W C) 160 W D) 0 W E) 120 W