A dam is thicker at the bottom than at the top mainly because
A) water is denser at deeper levels.
B) water pressure increases with depth.
C) surface tension exists only on the surface of liquids.
D) it looks better.
E) none of the above
Answer: B
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In expressions like ?v and ?t, ? stands for
a. "change in". b. "triangle". c. a constant of proportionality. d. a variable.
Neglecting recoil of the gold nucleus, how much kinetic energy must an alpha particle (charge = 2 × 1.6 × 10^–19 C) have to approach to within 5.70 × 10^?14 m of a gold nucleus (charge = 79 × 1.6 × 10^?19 C)? (ke = 8.99 × 10^9 N?m2/C2 and 1 MeV = 1.6 × 10^?13 J)
a. 4.4E–10 MeV b. 1.1E+1 MeV c. 2.0E+0 MeV d. 4.0E+0 MeV e. 5.0E–2 MeV
As a result of friction between internal parts of an isolated system
a. the total mechanical energy of the system increases. b. the total mechanical energy of the system decreases. c. the total mechanical energy of the system remains the same. d. the potential energy of the system increases but the kinetic energy remains the same. e. the kinetic energy of the system increases but the potential energy of the system remains the same.
Why do compasses point north?
a. Because the Coriolis force tends to force to point to the North Pole. b. Because Earth is a magnet with a magnetic north pole near the geographic North Pole. c. Because Earth is a magnet with a magnetic south pole near the geographic North Pole. d. Because the Earth is unmagnetized but its atmosphere is magnetic, especially near the North Pole. e. Because the Coriolis force deflects magnetic field lines to the right.