- #1
toothpaste666
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Homework Statement
The Earth is not a uniform sphere, but has regions of varying density. Consider a simple model of the Earth divided into three regions-inner core, outer core, and mantle. Each region is taken to have a unique constant density (the average density of that region in the real Earth):
a) Use this model to predict the average density of the entire Earth (use 4 sig figs).
b) The measured radius of the Earth is 6371 km and its mass is 5.974×1024kg. Use these data to determine the actual average density of the Earth (use 4 sig figs).
The Attempt at a Solution
using the info from the chart the inner core has a radius of 1220km. The Earth has a radius of 6371km so the fraction of the radius of the Earth that belongs to the inner core is
(1220km/6371km)= .1915
multiply this by the density of that region
(13000)(.1915)= 2489.5
now I do the same for each other region and add the results:
outer core = 3480km-1220km = 2260km
(2260km/6371km) = .3547
(.3547)(11100) = 393.7
mantle = 6371km-3480km = 2891km
(2891km/6371km) = .4538
(.4538)(4400) = 1997
1997 + 393.7 + 2489.5 = 4880.2 which to 4 sig figs is 4880.
mastering physics says i am wrong. Where did I go wrong? please help