Hi
work out volume of sphere 4/3 x Pi x radius power of 3
i work it out at approx 14 CM cubed
then density of iron is 7.8g per cm power of 3
approx =112 But I am doing rough calculations here and i might be out a power of 10
weigh your ball and this will tell you if ball is filled with less dense substance
if scraping black stuff I would advise against using metal, and if me i would do it under water, just to be certain
Regards
Ken
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