Question

3a. A planet that keeps the same hemisphere pointed towards the Sun must rotate once per orbit in the prograde direction. Draw a diagram to demonstrate this fact. The rotational period in an inertial frame, the sidereal day, for such a planet is equal to the orbital period, the length of the solar day on such a planet is infinite (this is known as being tidally locked). b. If a planet rotated once per orbit in the retrograde direction, how many solar days would it have per orbit? c. Earth rotates in the prograde direction. How many times must Earth rotate per orbit for there to be 365.24 solar days per year? Verify your result by comparing the length of Earth's sidereal rotational period 23 hours and 56 minutes) with the length of a mean solar day (24 hours). d. Determine a general formula relating the lengths of the solar and sidereal days on a planet. Use your formula to compute the lengths of solar days on Mercury, Venus, and Mars. e. For a planet on an eccentric orbit, the length of either the solar day or the sidereal day varies on an annual cycle. Which one varies, and why?

Answer 1

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