What is the common trait of all main-sequence stars?
A) They generate energy through hydrogen fusion in their core.
B) They are in the final stage of their lives.
C) They are all spectral type G.
D) They all have approximately the same mass.
A) They generate energy through hydrogen fusion in their core.
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The distance traveled by a wave during a single period is
A) one-half wavelength. B) one wavelength. C) two wavelengths. D) none of the above
Communications and weather satellites always appear at the same place in the sky because these satellites are
A) beyond the pull of Earth's gravitational field. B) moving at a speed just short of escape velocity. C) orbiting Earth with a 24-hour period. D) stationary in space. E) none of the above
Force on a Moving Charge: A proton, moving north, enters a magnetic field. Because of this field, the proton curves downward. We may conclude that the magnetic field must have a component
A. downward. B. upward. C. towards the east. D. towards the west. E. towards the north.
Typically, the new Moon's shadow _______ a solar eclipse
a. passes north of Earth so as NOT to produce b. passes south of Earth so as NOT to produce c. passes either north or south of Earth so as NOT to produce d. touches the Sun so as to produce e. touches Earth so as to produce