This is one of my homework problems for my mechanical engineering class. The problem is extremely simple, but, the homework is graded in this class and I want a good grade :). I should be able to do this no problem but I am getting confused by what some of the reading in my book is telling me. 1. The problem statement, all variables and given/known data As shown in given figure, a cylinder of compacted scrap metal measuring 2m in length and 0.5m in diameter is suspended from a spring scale at a location where the acceleration of gravity is 9.78 m/s2. If the scrap metal density in kg/m3, varies with position z, in m, according to p = 7800-360(z/L)2, determine the reading of the scale in Newtons. Cylinder diameter=.5m Cylinder height=2m G=9.78m/s2 http://img30.imageshack.us/img30/3094/0903091713.jpg [Broken] 2. Relevant equations F=mg Volume of Cylinder= 3.14r2*H Density=M/V Density of cylinder=7800-360(z/L)2 3. The attempt at a solution I already found the volume which is .3925m3. What I would normally do is solve for mass using the d=m/v equation. But my book says mass=[tex]\int[/tex](p)dV. It also says that "density, p, at a point is defined as, p = lim(from v to v')m/V". I have taken physics and lots of math but using limits and integrals for finding masses and densities is throwing me off.