During the period each year when we see Mars undergoing apparent retrograde motion in our sky, what is really going on in space?
A) Mars is moving around the Sun in the opposite direction from which Earth is moving around the Sun.
B) Earth and Mars are getting closer together.
C) Earth is catching up with and passing by Mars in their respective orbits.
D) Earth and Mars are on opposite sides of the Sun.
C) Earth is catching up with and passing by Mars in their respective orbits.
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The sunspot cycle affects I. the latitude at which sunspots are visible at a given time. II. the number of sunspots that are visible at a given time. III. the rotation rate of the Sun's equator at a given time. IV. the magnetic polarity of the sunspots at a given time
a. I & II b. I & IV c. II & III d. I, II & III e. I, II, & IV
When does a protostar become a main-sequence star?
A) when the rate of hydrogen fusion becomes high enough to balance the rate at which the star radiates energy into space B) when a piece of a molecular cloud first begins to contract into a star C) when it becomes luminous enough to emit thermal radiation D) at the instant that the first hydrogen fusion reactions occur in the protostar's core
On a winter day the temperature is 5 degrees Celsius and the humidity is 0.003 kilograms per cubic meter. (a) What is the relative humidity? (b) The air is brought into a building and heated to 20 degrees Celsius without changing the humidity. What is the relative humidity inside the building?
If a conductor is in electrostatic equilibrium near an electrical charge:
a. the sum of all forces between the conductor and the charge must be zero. b. the total charge on the conductor must be zero. c. any charges on the conductor must be uniformly distributed. d. the electric field inside the conductor must be zero.