The efficiency of a Carnot engine operating between 100°C and 0°C is most nearly:
a. 7%.
c. 27%.
b. 15%.
d. 51%.
C
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During the first moments of the big bang when elements could be created, nuclear fusion reactions made few heavy elements because
a. all heavy nuclei are unstable. b. no stable nuclei exist with masses of 5 or 8 hydrogen masses. c. the helium nucleus is unstable. d. the temperature and density were too low. e. no nuclei heavier than helium could form since there weren't any electrons formed.
Answer the following statement(s) true (T) or false (F)
1. Consider the electric field shown below:
This is a physically possible static electric field (that is, we can calculate a well-defined potential difference between any two points in this field).
2. Consider the electric field shown below:
(This hypothetical field is uniform to the left of the boundary shown and zero to the right of that boundary.) This is a physically possible static electric field (that is, we can calculate a well-defined potential difference between any two points in this field)
In Ptolemy's theory, retrograde planetary motion is explained as
A) the backward part of the planet's loop-the-loop orbits around Earth. B) due to the back-and-forth or "oscillatory" motion that planets make as they move along their circular orbits around Earth. C) due to the natural wandering of the celestial sphere of background stars. D) a result of Earth's motion: as Earth passes another planet, that planet appears to move backward as seen against the background stars. E) Actually he didn't have an explanation for this.
The energy of a photon of wavelength 400 nm is _____________.
a. 
b. 
c. 
d. 
e. 