SOLUTION: I need to make a spear head equal to that of Goliath in the Bible. We know it weighed around 15 lbs and was made of iron. Well, the best we can tell. So I know that 15 lbs of c

Question 823904: I need to make a spear head equal to that of Goliath in the Bible. We know it weighed around 15 lbs and was made of iron. Well, the best we can tell.
So I know that 15 lbs of cast iron would equal 240 oz.
We know that cast iron weighs 4.166666666666667 oz per cubic inch? (450 lbs per cubic foot = 7,200 oz / 1728 inches per cubic foot = 4.166666666666667)
If my math is right, we are looking at 57.6 cubic inches of cast iron would be 15 lbs.
So to get an idea of how big I need to make the spear head, lets say it is almost a cone shape 4 inches at the wide end. How long would it need to be?
Cone volume = 57.6 cubic inches
Cone base = 4 inches
Cone height = ???
I will need to make a prototype. Use that to disperse water to the 57.6 volume. Then make a mold and cast the iron. I know the cone height will actually be short of what I need but at this point I don't have a clue how long it needs to be. At least this should get me into the ball park. From there I will keep working on it until I end up with the 57.6 or a bit more.
If you see any error in my math up to this point, please let me know.
Kind of a fun project you will have to admit. Thanks a bunch.
Answer by ankor@dixie-net.com(22740) (Show Source): You can put this solution on YOUR website!
Cone volume = 57.6 cubic inches
Cone base = 4 inches
Cone height = ???
:
The volume of a cone: V = *
Assuming the diameter of the base of the cone = 4 inches, r=2 inches
*
multiply both sides by 3

divide both sides by
h =
h = 13.75 inches
:
A cone with a volume of 57.6, and a diameter of 4 will be 13.75 inches long

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