# Many people know that the weight of an object varies on different planets, but did you know that the weight of an object on Earth also varies according to the elevation of the object? In particular, the weight of an object follows this equation: w=Cr^-2 , where C is a constant, and r is the distance that the object is from the center of Earth.

a.Solve the equation w=Cr^-2 for r. The answer I came up with is r^-2=w/C: is this correct?
b.Suppose that an object is 100 pounds when it is at sea level. Find the value of C that makes the equation true. (Sea level is 3,963 miles from the center of the Earth.)
Thank you!

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1. Ok, I went back and tried again. The equation I found when solving for r is r=sqrt(C/w)
Is this correct?
Then in b I would plug in the 100 for w, and the 3,963 for r to find the constant, C, correct?

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2. a is correct.

C = w/r^-2

w = 100

r = 1/(3963)^2

Solve for C.

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3. So would my equation be C=100/(3963)^2 ...I'm confused

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4. Please let me know if I did this correct for b...
100=C/(3,963)^2
100=C/15,705,369
100*C=(C/15,705,369)*C
100C=15,705,369
100C/100=15,705,369/100
C=157,053.69

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