A substance composed of two or more elements chemically combined in a definite, fixed proportion by mass is
a. a molecule.
b. a compound.
c. an ion.
d. a mixture.
b
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Energy balance in the Sun refers to a balance between
A) the rate at which fusion generates energy in the Sun's core and the rate at which the Sun's surface radiates energy into space. B) the mass that the Sun loses each second and the amount of mass converted into energy each second. C) the force of gravity pulling inward and the force due to pressure pushing outward. D) the amount of energy the Sun radiates into space and the amount of energy that reaches Earth.
An electron is released from rest at a distance of 9.00 cm from a proton. If the proton is held in place,
how fast will the electron be moving when it is 3.00 cm from the proton? (mel = 9.11 x 10-31 kg, e = 1.60 × 10-19 C, k = 1/4??0 = 8.99 × 109 N ? m2/C2) A) 75.0 m/s B) 106 m/s C) 1.06 × 103 m/s D) 4.64 × 105 m/s E) 130 m/s
While the government cannot guarantee health and safety for each individual, its role is to provide for maximum health and safety for the community as a whole.
a. true b. false
Why do most extrasolar planets discovered by the Doppler method have orbits relatively close to their host stars?
A) They transit more frequently and have thus been more likely to be detected in the short time we have been searching for them. B) More of the starlight is blocked by the planet when it transits the star. C) These close-in planets are easier to detect because they cause larger Doppler shifts. D) The closer to a star, the hotter and therefore brighter the planet is. E) Planets that are close to a star are heated up and therefore larger.