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Mars has two moons. One of them orbits with a period of 7 hours 30 minutes at an orbital radius of 9.0 * 10³ km. Determine the mass of Mars, given that 4*pi²/G = 6 * 10¹¹ N⁻¹ m⁻² kg².

1. 5.96 * 10¹⁹ kg
2. 3.25 * 10²¹ kg
3. 7.02 * 10²⁵ kg
4. 6.00 * 10²³ kg

Correct answer: 6.00 * 10²³ kg

Solution

From Kepler's third law for a satellite, M = (4*pi²/G)*R³/T². Plug in the given constant, R in metres, and T in seconds.

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