Find Radius to Calculate Mass of Moon

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In summary, the conversation discusses the problem of finding the mass of the moon based on the radius and velocity of the Apollo 8 capsule in circular orbit above its surface. The individual is having trouble finding the correct velocity and is seeking help to solve the problem. They mention using the equation v=2(pi)r/T, but are unsure of how to find the radius. After some discussion, it is determined that the radius of the orbit should be 1.74 x 10^6 m + 112 km. The conversation ends with a suggestion to use the concept of centripetal force to solve the problem.
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ucdawg12
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Okay, I'm having some trouble getting radius I need for the velocity that I need to solve this problem:

The manned Apollo 8 capsule was put into circular orbit 112km above the surface of the moon. The period of the orbiting space capsule was 120.5 minutes. If the radius of the moon is 1.74x10^6m, what is the mass of the moon.

Now I know how to find the mass of the moon once I get the velocity, but for some reason my velocity is coming out all wrong. I am doing v=2(pi)r/T, I know T=120.5x60= 7230seconds but I can't figure out how to find the radius. I have in my notes its 1850000m but of course I left out how I got to that and I think I have tried every combonation of numbers I have and still can't get it.

Thanks
 
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  • #2
Isn't the radius of the orbit just 1.74 x 10^3 + 112 km?
 
  • #3
omfg... i could have sworn those were first numbers I tried, I must have messed up somewhere on the calculator...
thanks, and sorry
 
Last edited:
  • #4
Hehe :smile:. I guess you might not have converted the 112 km into metres, or the Moon's radius into km?
 
  • #5
Well,Nylex,i'm surprised you haven't suggested him how to solve the problem...

Think that the gravity force (exerted by the moon on the satellite) is a centripetal force...

Daniel.
 

What is the formula for finding the radius of the moon to calculate its mass?

The formula for finding the radius of the moon to calculate its mass is: Mass of Moon = (4/3) x (pi) x (radius of moon)^3 x (density of moon).

What is the density of the moon?

The density of the moon is approximately 3.34 grams per cubic centimeter.

Why is finding the radius of the moon important in calculating its mass?

Finding the radius of the moon is important in calculating its mass because the mass of an object is directly proportional to its radius. The larger the radius, the larger the mass will be.

How is the radius of the moon measured?

The radius of the moon is measured using various methods such as satellite imagery, laser altimetry, and radar mapping. These methods allow scientists to accurately determine the size and shape of the moon.

What other factors besides radius and density influence the mass of the moon?

Other factors that influence the mass of the moon include its composition, gravitational pull, and any external forces acting upon it such as the Earth's gravitational pull and the gravitational pull of other celestial bodies.

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