Posted by **help please** on Sunday, December 11, 2011 at 7:37pm.

You have arrived at a new planet and put your starship into a circular orbit at a height above the surface that is equal to two times the radius of the planet. Your speed is 4300 m/s and it takes 7 hours and 18 minutes to complete an orbit.

a. What is the radius of the planet?

b. What is the mass of the planet?

- physics -
**drwls**, Sunday, December 11, 2011 at 8:57pm
a. Let R be the radius of the orbit and R' be the radius of the planet.

V *7.3 min*60 sec/min = 2*pi*R

Solve for R, then use R' = R/2.

b. G*M/R^2 = V^2/R

Solve for M

- physics -
**Anonymous**, Sunday, December 11, 2011 at 9:45pm
for the second equation use R, not R' correct?

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