finding values: Solve 'w = Cr^-2' for r; find value of C

[kittiecs]

I am having a problem with the following problem:

The weight of an object follows the equation w = Cr^-2, where C is the constant and r is the distance that an object is from the center of the Earth.

The first problem was to solve the equation w = Cr^-2 for r. My answer is w=c/r^2

The question I am having a problem with is this one:

If the object is 100 pounds at sea level, find the value of C that makes the equation true.

I need help with how I should find the value of C. (Sea level is 3963 miles from the center of the earth.
thank you

 

[galactus]

You seem to have gone astray in your solving for r.

\(\displaystyle \L\\W=\frac{c}{r^{2}}\)

\(\displaystyle \L\\r=\sqrt{\frac{c}{w}}\)

Now, you can use either equation. Set r=3963 and w=100 and solve for c.