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12-10-2007, 12:36 PM
Forensic pathology question:
Three flakes of lead:
1) 0.5 mm in diameter,
2) 1.0 mm in diameter,
3) 2.0 mm in diameter,
each 0.5 mm thick.
How much do they weigh total, in grains?
12-10-2007, 12:56 PM
12-10-2007, 01:16 PM
Assume they're roughly cylindrical.
Volume of a cylinder is pi*r2*height
The radii are .025 cm, .05 cm, and .1 cm.
pi*0.000625*.05 = .000098 cm3
pi*0.0025*.05 = 0.00039 cm3
pi*0.01*.05 = 0.00157 cm3
density of elemental lead is 11.34 gram/cubic centimeter
=0.00111 g or 1.11 mg
=0.00442 g or 4.42 mg
=0.0178 g or 17.8 mg
Total 23.3 mg
a grain is 64.80 mg
ON PREVIEW - That's pretty amazing we came to the same answer, yoyodyne!
12-10-2007, 01:21 PM
How many answers are there?
12-10-2007, 01:40 PM
How many answers are there?Well, there's the one where I move the decimal the wrong number of places, but I didn't give that one. (I don't think...)
Or there's the one where one doesn't assume the flakes are cylindrical. But I didn't give that one.
Then there's another where one makes a rounding or significant figures error. Actually, it's possible we both gave that one....
12-10-2007, 02:33 PM
Thank you, yoyodyne and Randy, for those quick and matching answers.
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