The discovery of the cosmic microwave background was important because:
A) it established a firm center of the Universe.
B) it was experimental verification of a prediction from the Big Bang theory.
C) it proved that astronomy at radio wavelengths was possible.
D) its detection was a major advance in microwave testing.
E) it showed the universe must be closed, with more than the critical density here.
B
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Radiation Doses: The maximum permissible workday dose for occupational exposure to radiation is 11 mrem. A 77-kg laboratory technician absorbs 2.3 mJ of 0.5-MeV gamma rays in a work day. The relative biological effectiveness (RBE) for gamma rays is 1.00. What is the number of gamma-ray photons absorbed by the technician in a workday?
A. 3 × 1010 B. 3 × 109 C. 3 × 108 D. 1 × 109 E. 1 × 108
A rod system with a uniform linear density of l = 4.40 kg/m has the shape shown in the figure, with rod 1 the vertical rod and rod 2 the horizontal rod. Rod 1 has length L1 = 8.00 m, and rod 2 has length L2 = 7.50 m. Neglect the diameter of the rods
?
What is the mass of each rod?
a.
rod 1: 12.4 kg, rod 2: 11.9 kg
b.
rod 1: 4.69 kg, rod 2: 4.13 kg
c.
rod 1: 0.550 kg, rod 2: 0.587 kg
d.
rod 1: 35.2 kg, rod 2: 33.0 kg
The electric flux through the two adjacent spherical surfaces shown below is known to be the same
It is also known that there is no charge inside either spherical surface. We can conclude that
a.
there is no electric field present in this region of space.
b.
there is a constant E field present in this region of space.
c.
the electric flux has a constant value of zero.
d.
any of the above may be correct.
e.
only (a) and (b) above may be correct.
A particle (mass = 5.0 g, charge = 40 mC) moves in a region of space where the electric field is uniform and is given by Ex = ?5.5 N/C, Ey = Ez = 0 . If the position and velocity of the particle at t = 0 are given by x = y = z = 0 and vx = 50 m/s, vy = vz = 0, what is the distance from the origin to the particle at t = 2.0 s?
a. 60 m b. 28 m c. 44 m d. 12 m e. 88 m