Here's the problem i've been working on.(adsbygoogle = window.adsbygoogle || []).push({});

Gold has density of 19.3x103 kg/m3. How big would a solid gold sphere have to be if the acceleration due to gravity at its surface is to be 9.87 m/s2? (Check your answer against the radius of the Earth, which has a mean density of 5.5x103 kg/m3.)

Now I'm probably making this way to hard, and I am completely lost, and was wondering if anyone could help me out. The only way i could think to do this problem, was to calculate out the mass, then the radius, and volume of the earth. Then use the density of gold to find out how large a gold ball would have to be to be the same weight as earth.

But then when i get the radius of the gold ball and plug it into the equation g=G*(Me/Re^2) which should equal 9.87, but it equals like 15. so i know i screwed up somewhere.

I just cant think of how to do this problem.

any help is much appreciated

**Physics Forums | Science Articles, Homework Help, Discussion**

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Gravitation problem

**Physics Forums | Science Articles, Homework Help, Discussion**