A 0.14-km wide river flows with a uniform speed of 4.0 m/s toward the east. It takes 20 s for a boat to cross the river to a point directly north of its departure point on the south bank. What is the speed of the boat relative to the water?
a. 5.7 m/s
b. 8.5 m/s
c. 8.1 m/s
d. 7.0 m/s
e. 6.4 m/s
c
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A hydrogen bond is:
a. a sharing of a pair of electrons between a hydrogen and an oxygen nucleus b. a sharing of a pair of electrons between a hydrogen nucleus and either an oxygen or a nitrogen nucleus c. a weak attraction between a covalently bonded hydrogen atom and another atom taking part in a separate polar covalent bond d. the loss of an electron by hydrogen to a highly electronegative atom e. a strong chemical bond between two ions
How do astronomers think Saturn generates its internal heat?
A) radioactive decay B) internal friction due to its high rotation rate C) chemical processes D) by raining dense helium droplets from higher to lower altitudes, resembling the process of differentiation E) nuclear fusion in the core
Given that white dwarf supernovae are such good standard candles, why don't we use them to measure the distance to all galaxies?
A) They are rare events, so we have observed them in only a tiny fraction of all galaxies. B) We cannot see them beyond a distance of about 100 million light-years. C) They can occur only in spiral galaxies, not elliptical galaxies. D) We would, but we don't have enough telescopes.
Velocity: A polar bear starts at the North Pole. It travels 1.0 km south, then 1.0 km east, and then 1.0 km north to return to its starting point. This trip takes 45 min. What was the bear's average velocity?
A. 0.00 km/h B. 0.067 km/h C. 4.0 km/h D. 5.3 km/h