By approximately _________ years ago, _________ had produced oxygen in enough amounts to be a significant fraction in Earth's atmosphere.
a. 100 million; trees and plants
b. 1 billion; trees and plants
c. 250 million; bacteria and algae
d. 2.5 billion; bacteria and algae
e. 2,000; animals and humans
c. 250 million; bacteria and algae
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A charge per unit length given by ?(x) = bx, where b = 12 nC/m2, is distributed along the x axis from x = +9.0 cm to x = +16 cm. If the electric potential at infinity is taken to be zero, what is the electric potential at the point P on the y axis at y = 12 cm?
A. 5.4 V B. 7.2 V C. 9.0 V D. 9.9 V E. 16 V
A barge with vertical sides is 10.0 m wide and 60.0 m long and is floating in fresh water. How much deeper into the water does the barge sink when 300,000 kg of coal are loaded on the barge?
A) 25.0 cm B) 50.0 cm C) 75.0 cm D) 1.00 m E) 1.50 m
The wave-particle duality applies to
A) photons. B) electrons. C) protons D) all of the above E) none of the above
Which of the following features of a telescope determines its light gathering power?
a. The focal length of the objective b. The focal length of the eyepiece c. The diameter of the objective d. Length of the telescope tube e. None of the above.