Because almost all galaxies show redshifted spectra, we know that
A) the sky must be dark at night.
B) the universe is expanding.
C) our understanding of redshift is wrong.
D) we must be at the center of the universe.
E) the universe is closed.
B
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The resistance of a platinum wire is to be calibrated for low-temperature work. A platinum wire with resistance 1.5 ? at 30°C is immersed in liquid nitrogen at 93 K (?180°C). If the temperature response of the platinum wire is linear, what is the expected resistance of the platinum wire at ?180°C? [?platinum = 3.92 × 10^?3 (°C)?1]
a. 0.265 ? b. 2.38 ? c. 2.73 ? d. 8.48 ? e. 0.618 ?
Consider a plot of the displacement (x) as a function of the applied force (F) for an ideal elastic spring. The slope of the curve would be
A) the acceleration due to gravity. B) the spring constant. C) the reciprocal of the acceleration of gravity. D) the mass of the object attached to the spring. E) the reciprocal of the spring constant.
One end of a copper rod is in thermal contact with a hot reservoir at T = 500 K and the other end is in thermal contact with a cooler reservoir at T = 300 K. Find the entropy change of each reservoir, and the total entropy change, when 8000 J of heat energy are conducted from one end of the rod to the other with no change in the temperature distribution in the rod
A student weighing 700 N climbs a flight of stairs 5.0 m high. Calculate the work done