What evidence do we have that life arose fairly quickly on Earth?
What will be an ideal response?
Answer: Because of the period of heavy bombardment, it would have been difficult for life to survive more than about 4 billion years ago. Combined with evidence from fossils of life 3.5 billion years ago and carbon isotope evidence dating back to 3.95 billion years, it seems that it only takes a few hundred million years for life to spring into existence.
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A hair dryer draws 1 350 W, a curling iron draws 700 W, and an electric light fixture draws 550 W. If all three of these appliances are operating in parallel on a 120-V circuit, what is the total current drawn?
a. 7.22 A b. 21.7 A c. 2.09 A d. 27.5 A e. 11.3 A
The approximate size of the nucleus in an atom is
a. 10-8 m. b. 10-10 m. c. 10-12 m. d. 10-15 m. e. 10-18 m.
All the following statements about Mars are true. Which one might be the cause of a significant loss of atmospheric gas to space?
A) The rock on Mars is probably red because of chemical reactions with oxygen that had been released into the atmosphere through the outgassing of water molecules. B) Mars lost its global magnetic field, leaving the atmosphere vulnerable to the solar wind. C) The axis tilt of Mars is thought to change significantly with time. D) Mars probably once had a much higher density of greenhouse gases in its atmosphere than it does today.
Kirchhoff's Rules: A multiloop circuit is shown in the figure. Find the current I2 if the batteries are ideal. (It is not necessary to solve the entire circuit.)
A. -3 A B. 3 A C. 7 A D. -7 A E. 0 A