Math 106-01: Calculus II: Reading Homework 8.2

1. Density and Center of Mass : what is this section concerned with? ``density'' alone is not a good answer for this.
   
   1. Density Calculation : how do we divide a region to calculate its density?
      
      1. examples : how is the mass of a column of air calculated? why is it sliced as it is? how is the population of a circular city calculated?
         
   2. Center of Mass : what is the center of mass of something? what is the moment of a mass? how does this translate to a Riemann sum?