The alternating current in wide use in homes in North America is 60 cycles per second, or 60 Hz. How many times per minute does this current reverse its direction of travel?
A. 3600 times
B. 60 times
C. 7200 times
D. 120 times
E. None of these choices are correct
Answer: C
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Venus's extremely high surface temperatures are due to
A. a recent impact that heated the planet. B. the composition of its atmosphere. C. volcanic activity. D. its relatively close proximity to the Sun.
When white light illuminates a green leaf, ________________ are the two colors of light that are mainly absorbed.
a. Blue and Yellow b. Green and Yellow c. Green and Red d. Red and Blue
Although the entire universe may be much larger than our observable universe, we can see only within our observable universe. The "boundary" of our observable universe is called
A) the cosmological horizon. B) the Big Bang. C) the lookback time. D) the Hubble Deep Field.
A simple pendulum has a mass of 0.50 kg and a length of 1.0 m. It is displaced through an angle of 30° and then released. After a time, the maximum angle of swing is only 10°. How much energy has been lost to friction?
a. 2.0 J c. 0.66 J b. 1.6 J d. 0.58 J