SOLUTION: an alloy was machined into a flat disk 31.5 mm in diameter and 4.5 mm thick. a hole 7.5 mm in diameter was drilled through the center. the disk weighed 20.2 g. what was the density

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Question 893227: an alloy was machined into a flat disk 31.5 mm in diameter and 4.5 mm thick. a hole 7.5 mm in diameter was drilled through the center. the disk weighed 20.2 g. what was the density of the alloy in SI units?
Answer by Fombitz(32388) About Me  (Show Source):
You can put this solution on YOUR website!
Find the volume of the new part.
The volume is the difference of the two circular areas multiplied by the thickness.

V=1053pimm%5E3
Converting to m%5E3,
V=1053pi%2A10%5E%28-9%29m%5E3
The mass in kg would be
m=20.2%2F1000=2.02%2A10%5E%28-2%29kg
So the density is,
rho=m%2FV=%282.02%2A10%5E%28-2%29%29%2F%281053pi%2A10%5E%28-9%29%29
rho=6106kg%2Fm%5E3