You start with a sample of 14C that contains 200 atoms. After three half-lives, how many atoms of 14C will be left?
A. 25
B. 50
C. 75
D. 100
E. 150
A. 25
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Which of the following seems to be a region of self-sustaining star formation?
A) The Orion complex B) The asteroid belt C) The Kuiper Belt D) The Solar System
Most SETI searches are done at:
A) X-ray wavelengths. B) infrared wavelengths. C) visual wavelengths. D) radio wavelengths. E) gamma wavelengths.
A solid metal sphere is 15.0 cm in diameter and has surface of uniform color. When its surface is at 112°C, you measure that it radiates energy at a rate of 71.3 W
What is the emissivity of the surface of this object? Any heat that enters the sphere from the outside environment is negligible. The Stefan-Boltzmann constant is 5.670 × 10-8 W/m2 • K4.
A parallel-plate capacitor stores charge Q. The capacitor is then disconnected from its voltage source, and the space between the plates is filled with a dielectric of constant ? = 2 . What is the relationship between the stored energies of the capacitor, where PEi is the initial stored energy, and PEf is the stored energy after the dielectric is inserted?
a. PEf = 0.25PEi b. PEf = 0.5PEi c. PEf = PEi d. PEf = 2PEi