According to current science, why didn't oxygen begin to accumulate in the atmosphere for more than a billion years after life appeared on the Earth?
A) Oxygen released by life was removed from the atmosphere by chemical reactions with surface rocks until the surface rock could absorb no more.
B) Early forms of animal life consumed the oxygen released by plants during the first billion years of life on Earth.
C) Early life did not release oxygen, and oxygen-releasing organisms didn't evolve for a billion years after the earliest life.
D) Oxygen released by life was removed from the atmosphere by dissolving in the ocean until the oceans could dissolve no more.
A) Oxygen released by life was removed from the atmosphere by chemical reactions with surface rocks until the surface rock could absorb no more.
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Based on DNA studies, it seems that all life on Earth
A) shares a common ancestor. B) belongs to one of just two kingdoms: plants and animals. C) arose from one of five distinct ancestors that lived about 2 billion years ago. D) requires oxygen to survive.
Determine the rate of heat transfer per unit length from a 5-cm-OD pipe at 150°C placed eccentrically within a larger cylinder of 85% Magnesia wool as shown in the sketch. The outside diameter of the larger cylinder is 15 cm and the surface temperature is 50°C.
GIVEN
A pipe placed eccentrically within a larger cylinder of 85% Magnesia wool as shown in the sketch
Outside diameter of the pipe (Dp) = 5 cm = 0.05 m
Temperature of the pipe (Ts) = 150°C
Outside diameter of the larger cylinder (Do) = 15 cm = 0.15 m
Temperature of outer pipe (To) = 50°C
FIND
The rate of heat transfer per meter length (q)
ASSUMPTIONS
Two dimensional heat flow (no end effects)
The system is in steady state
Uniform thermal conductivity
SKETCH
If the acceleration vector of an object is directed anti-parallel to the velocity vector, then
A) the object is speeding up. B) the object is slowing down. C) the object is turning. D) the object is at rest. E) this situation would not be physically possible.
Suppose that the temperature of the solar nebula had been much colder. How might the Solar System look different today?
A) Terrestrial planets may have formed at a larger distance from the Sun. B) The gas giant planets might be bigger and farther from the Sun. C) The gas giant planets might be bigger and closer to the Sun. D) More planets would have formed.