A rising balloon is buoyed up with a force equal to the
A) weight of air it displaces.
B) density of surrounding air.
C) atmospheric pressure.
D) weight of the balloon and its contents.
E) all of the above
Answer: A
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Magnetic Field of a Current Loop: Consider two current-carrying circular loops. Both are made from one strand of wire and both carry the same current, but one has twice the radius of the other. If the magnetic field strength at the center of the smaller loop is B, what is the magnetic field strength at the center of the larger loop?
A. 8B B. 4B C. 2B D. B/2 E. B/4
Moonquakes on the Moon were detected by
A) the radar observations over time from Earth. B) the seismographs left these by the Apollo astronauts. C) laser beams reflected off mirrors left on the Moon by Apollo missions. D) seismographs attached to the Russian Lunar rovers. E) telescopic observations of lunar landslides.
A thin spherical shell of radius 20.0 cm has 5.0 ?C of charge uniformly distributed over its surface. What is the electric flux through an area of 1.00 m2 of a spherical surface concentric with the shell of charge but having a radius of 1.00 m?
a. 
b. 
c. 
d. 
e. 0
What is one piece of evidence that some organelles like mitochondria and chloroplasts within eukaryotes used to be independent prokaryotes that were incorporated into eukaryotic cells?
A) the DNA inside organelles is not made of the same four bases as the DNA in the host cells B) organelles float around independently inside eukaryotic cells C) prokaryotes are seen incorporating into cells today D) organelles are very similar to present-day bacteria, suggesting a common ancestor