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Homework Help: Gravitation physics homework

  1. Jan 24, 2008 #1
    1. The problem statement, all variables and given/known dataYour starship, the Aimless Wanderer, lands on the mysterious planet Mongo. As chief scientist-engineer, you make the following measurements: a 2.50-kg stone thrown upward from the ground at 11.0 returns to the ground in 9.00 ; the circumference of Mongo at the equator is 2.00×10^5 ; and there is no appreciable atmosphere on Mongo. I found the mass to be 3.71*10^25, now part B asks me for..."If the Aimless Wanderer goes into a circular orbit 3.00×104 above the surface of Mongo, how many hours will it take the ship to complete one orbit?"

    2. Relevant equations F_g = (GM1M2)/R^2, g= GM/R^2, T^2=R^3, V=(2piR)/T

    3. The attempt at a solution I attempt to use the propotions rule where (T1^2/R1^3) = (T2^2/R^3) using this i have to calculate the period of the planet some how. I figured in order to do this i must need velocity of the planet. if the mass of the ship was given i would also be able to solve the problem so i attempted to use the equation F_g=(GM1M2)/R^2 but do not know F_g, I thought maybe this was F=ma therefore F=(3.71*10^25)(2.44) (2.44 was solved for a using kinematics.) Any help would be appreciated thanks.
  2. jcsd
  3. Jan 25, 2008 #2

    Shooting Star

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    Homework Helper

    At the given altitude,

    Fc = GMm/(R+h)^2, where Fc = mw^2(R+h). Find w and hence T directly.
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