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Astro 210 Exam 1 Practice Problems

# Astro 210 Exam 1 Practice Problems - Hour Exam 1 Review...

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Hour Exam 1: Review Questions Plausible questions: either from old exams, or at right level for this exam Telescopes must have “tracking” motors on them which rotate the scope to keep the same celestial objects in the field of view. Briefly (1-2 sentences) explain why a tracking motor is needed. Find the angular speed at which a telescope must rotate to track a star on the celestial equator. 1

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The celestial sphere and all objects on it rotates once a day realtive to a terrestrial observer. Thus a telescope pointing to a fixed direction relative to the horizon will see stars carried in and out of the field of view; to compenstate for the celestial sphere’s rotation, a motor must match its spin rate. The motor’s spin rate is that of the celestial sphere: covering a full circuit of Δ θ = 360 over a period of Δ t = P = 1 day, for an angular speed of ω = Δ θ Δ t = 360 P = 1 / day = 15 / hour = 0 . 25 / min (1) Since you were not asked to put your answer in a particular set of units, any of these units would be fine. 2
Saturn’s moon Titan orbits the planet with a semi-major axis of a = 1 . 2 × 10 9 m and a period P = 1 . 4 × 10 6 s. Using these data, calculate the mass of Saturn. The Sun is accelerated due to its interactions with the planets. Which is larger: the Sun’s acceleration due to its interaction with Earth, or the Sun’s acceleration due to its interaction with Jupiter? Show your work. Note that a Jup = 5 . 2 AU.

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Astro 210 Exam 1 Practice Problems - Hour Exam 1 Review...

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