The ionosphere reflects __________ frequency radio waves
Fill in the blank(s) with correct word
low
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What is the angular speed about the rotational axis of the Earth for a person standing on the surface?
a. 7.3 × 10^?5 rad/s b. 3.6 × 10^?5 rad/s c. 6.3 × 10^?5 rad/s d. 3.1 × 10^?5 rad/s
The primary source of the energy radiated by a star, such as the sun, is
A) fusion reactions in which helium is fused to form iron. B) fusion reactions in which hydrogen is fused to form helium. C) beta decay. D) fission reactions involving uranium. E) alpha decay.
One stone is dropped from the side of a bridge, and a second is dropped from the same place a short time later. What is true about the distance between the stones as a function of time after both have been dropped? Ignore air resistance
A. Increases, finally reaching a constant value B. Always increases C. Is constant D. Decreases, and then reaches a constant value E. Always decreases
The majority of lunar craters formed when ________.
A. tidal forces from Earth cracked the Moon's surface B. lunar volcanoes erupted C. pieces of the Moon fell off, leaving holes in its surface D. solid bodies such as asteroids impacted the Moon's surface