A soccer ball is kicked with a velocity of 25 m/s at an angle of 45° above the horizontal. What is the vertical component of its acceleration as it travels along its trajectory? (Neglect air friction.)
A) g sin(45°) upward
B) g downward
C) zero
D) g cos(45°) downward
E) g upward
B
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The number of comets in the Oort cloud is probably about
A) a thousand. B) a million. C) a billion. D) a trillion. E) a quintillion.
Why do astronomers believe that the Jovian planets are composed mainly of hydrogen and helium?
A. Because the Jovian planets have low densities. B. Because hydrogen and helium are the main constituents of the Solar System. C. Because the Jovian planets are very large. D. The Voyager missions measured the chemical compositions of the interiors of the Jovian planets.
Jim exerts a force of 500 N against a 100-kg desk that does not move. Virgil exerts a force of 400 N against a 60-kg desk that moves 2 m in the direction of the push. Mik exerts a force of 200 N against a 50-kg desk that moves 5 m in the direction of the push. The most work is done by
A. Jim. B. Mik. C. Virgil. D. Virgil and Mik, who do equal amounts of work.
Aline says that the magnetic moment of an atom originates in the orbital angular momentum of the electron. Bevis says that it comes from the electron spin. Which one, if either, is correct, and why?
a. Aline, because only atoms, not electrons, can have angular momentum. b. Bevis, because only atoms, not electrons, can have angular momentum. c. Neither, because electron spin and orbital angular momentum always cancel exactly. d. Neither, because the magnetic moment of an atom comes only from the spin of the nucleus. e. Both, because both the orbital angular momentum and the spins of the electrons contribute to the magnetic moment of an atom.