Why is the very center of Earth's core a solid and not a liquid?
a. There is less metal in the central core
b. The central core has a combination of gases with the metals.
c. Accretion "seeded" Earth with a solid central core.
d. The pressure at the central core raises the melting point of the metals higher than its temperature.
e. The central core is a frozen block of water ice.
d
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The Apollo and Aten asteroids have orbits that:
A) cross the orbit of Earth at perihelion. B) cross the orbit of Mars, but not the Earth, at perihelion. C) remain between Mars and Jupiter, in the main belt. D) stay sixty degrees ahead of or behind Jupiter. E) stay out beyond Neptune.
Whereas electric charges can be isolated, magnetic poles
A) can also. B) cannot. C) gather in clusters. D) none of the above
First Law of Thermodynamics: An external heat source supplies heat to a system at a rate of 187 W as the system does work at a rate of 131 W. At what rate is the internal (thermal) energy of the system changing?
A. -56 W B. 320 W C. 56 W D. 190 W E. -320 W
Two 10¢ coins (dimes) carrying identical charges are lying 2.5 m apart on a table. If an electrostatic force of magnitude 2.0 N is exerted on each coin by the other coin,
how large is the charge on each coin? (k = 1/4??0 = 9.0 × 109 N ? m2/C2 ) A) 2.6 ?C B) 26 ?C C) 6.7 ?C D) 5.2 ?C E) 52 ?C