Which of the following provides direct evidence that the chemical building blocks of life (such as amino acids and DNA bases) could have formed naturally under the conditions that were present on the early Earth?
A) Fossil remains of life date to fairly early in Earth's history.
B) These chemicals have been formed in laboratory experiments that recreate conditions of the early Earth.
C) DNA studies show that all known life on Earth evolved from a common ancestor.
D) We have found evidence of complex carbon molecules on Saturn's moon Titan.
B) These chemicals have been formed in laboratory experiments that recreate conditions of the early Earth.
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An electron is confined in a harmonic oscillator potential well. A photon is emitted when the electron undergoes a 3?1 quantum jump
What is the wavelength of the emission if the net force on the electron behaves as though it has a spring constant of 9.6 N/m? (mel = 9.11 × 10-31 kg, c = 3.00 × 108 m/s, 1 eV = 1.60 × 10-19 J, h = 1.055 × 10-34 J ? s, h = 6.626 × 10-34 J ? s) A) 290 nm B) 150 nm C) 190 nm D) 580 nm
Acceleration: Suppose that a car traveling to the west (-x direction) begins to slow down as it approaches a traffic light. Which statement concerning its acceleration must be correct?
A. Its acceleration is positive. B. Its acceleration is negative. C. Its acceleration is zero. D. Its acceleration is decreasing in magnitude as the car slows down.
When a liquid freezes
A) the temperature of the substance increases. B) the temperature of the substance decreases. C) heat energy leaves the substance. D) heat energy enters the substance.
Suppose the date is March 21 and the Sun passes through your zenith at noon. Where are you?
A) the equator B) the Tropic of Cancer (latitude 23-1/2°N) C) the Tropic of Capricorn (latitude 23-1/2°S) D) the Arctic Circle (latitude 66-1/2°N) E) the Antarctic Circle (latitude 66-1/2°S)