# Thread: Iverse variation of a function WP

1. ## Iverse variation of a function WP

The weight of a body in space varies inversely as the square of its distance from the center of the earth. If something weighs 5 lbs on the surface of the earth, how much does it weigh 1000 miles from the surface of the earth? The radius of the earth is 4,000 miles.

Would it be W= k/d^2 ? Could someone work this out for me.

Thanks

2. Originally Posted by na300zx
The weight of a body in space varies inversely as the square of its distance from the center of the earth. If something weighs 5 lbs on the surface of the earth, how much does it weigh 1000 miles from the surface of the earth? The radius of the earth is 4,000 miles.

Would it be W= k/d^2 ? Could someone work this out for me.

Thanks
$\displaystyle 5 = \frac{k}{4000^2}$

solve for $\displaystyle k$, then determine $\displaystyle W$ when $\displaystyle d = 5000$

3. Thanks for your reply. So the correct equation would be k= 80,000,000 W=80,000,000/5000^2 which equals 3.2 lbs?