Suppose that the Hubble constant had the value 35.0 km/s per million light-years
(1 y = 3.156 × 107 s, mH ? mproton = 1.67 × 10-27 kg, c = 3.00 × 108 m/s, 1 light-year = 9.461 × 1015 m, G = 6.67 × 10-11 N ? m2/kg2)
(a) What would be the maximum density the universe could have that would still allow it to expand forever?
(b) Under the conditions of part (a), how many hydrogen atoms would we expect to find, on the average, in a volume of space measuring 3.00 m by 8.00 m by 8.00 m?
(a) 2.45 × 10-26 kg/m3 (b) 2820 atoms
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Which variable is increasing the fastest on the graph prepared in Procedure 2?
A velocity selector uses a fixed electric field of magnitude E and the magnetic field is varied to select particles of various energies. If a magnetic field of magnitude B is used to select a particle of a certain energy and mass, what magnitude of magnetic field is needed to select a particle of equal mass but twice the energy?
a. 0.50 B b. 1.4 B c. 2.0 B d. 0.71 B e. 1.7 B
A loop of wire is rotated about a diameter (which is perpendicular to a given magnetic field.) In one revolution the induced current in the loop reverses direction how many times?
A) 0 B) 4 C) 2 D) 1 E) 3
Imagine a small magnet with its north pole vertically upward passing near the south pole of an external magnet that is above the small magnet. In what direction does the net force acting on the magnet point?
A. Upward. B. Downward. C. There is zero net force. D. None of the above (explain).