Three flakes of lead

[Walloon]

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?

[yoyodyne]

0.36

[Randy Seltzer]

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

=0.36 grains


ON PREVIEW - That's pretty amazing we came to the same answer, yoyodyne!

[yoyodyne]

How many answers are there?

[Randy Seltzer]

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....

[Walloon]

Thank you, yoyodyne and Randy, for those quick and matching answers.