Kepler's Laws: Let the orbital radius of a planet be R and let the orbital period of the planet be T. What quantity is constant for all planets orbiting the sun, assuming circular orbits?
A. T/R
B. T/R2
C. T2/R3
D. T3/R2
E. T2/R
Answer: C
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Which of the following statements is true of the spectral sequence?
A) It is classified in groups labeled A through Q. B) M stars are cooler and fainter than L dwarfs. C) Y dwarfs are a class of objects with temperatures above 500 K. D) O stars are the hottest, and M stars are the coolest.
Which of these were observed from Earth, prior to spacecraft missions to Mars?
A) seasonal changes in the polar caps B) eruptions of Mount Olympus C) dust storms capable of covering the entire planet D) Both A and C are correct. E) All of the above are correct.
Bert says that a charged particle in a vacuum can travel in a helix only if a uniform electric field and a uniform magnetic field are both present and both parallel to the axis of the helix. Stuart says that only a magnetic field with a component parallel to the axis of the helix is needed. Which one, if either, is correct, and why?
a. Bert, because the charged particle's velocity can have a vertical component only if an electric field in the vertical direction is present. b. Stuart, because a component of velocity in the vertical direction is not changed by a vertical component of a magnetic field. c. Bert, because a component of velocity in the vertical direction is changed by a vertical component of a magnetic field. d. Stuart, because an electric field in the vertical direction would cause the particle to come to a complete stop. e. Neither, because particles cannot move in helical paths in the presence of magnetic and electric fields.
No magnetic force acts on a current carrying wire when it
A) carries a very small current. B) is perpendicular to the magnetic field. C) either or both of these D) none of the above