# Iverse variation of a function WP

• Oct 25th 2009, 01:31 PM
na300zx
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
• Oct 25th 2009, 01:57 PM
skeeter
Quote:

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 $\displaystyle d = 5000$
• Oct 25th 2009, 03:27 PM
na300zx
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?