Link:http://output.to/sideway/default.asp?qno=120600013 Centroid of 3D Body Centroid of 3D BodyThe centroid of 3D Body is determined by the first moment of a three dimensional body with the method of the first moment of volume. ![]() Centroids of VolumesVolume by IntegrationAlthough triple integration is usually required to determine the volume of 3D body. However volume of 3D body can also be determined by performing a double integration or a single integration. Volume by Double IntegrationIf the inner integration of the unit elemental volume can be expressed as a strip of elemental volume in one dimension. ![]() For example, the signed volume of the 3D ellipic cylinder is bounded by surfaces in rectangular form , Imply ![]() An elemental volume ΔV in rectangular form can be defined as Δx times Δy times Δz. Imply ![]() An unit elemental volume can be expressed as ![]() Therefore the unit elemental volume can be expressed as a strip of elemental volume of the solid cylinder U in the planar region R of cartesian coordinates yz. Imply ![]() All unit elemental volumes can be bounded by curves in the plane yz. And the curves is ![]() In general, the volume of a region can be determined by double integration through sweeping the signed elemental volume starting from along either rectangular coordinate axes. Imply Starting from horizontal sweeping along y axis ![]() Consider an unit elemental volume ΔVyz along y axis horizontally. Imply ![]() Since the bounding curves are joined at plane zx, The bounds of the bounding curves are ![]() Therefore the volume of the solid cone U can be determined by ![]() Therefore the volume of the solid cone U is ![]() Volume by Single IntegrationIf the inner integration of the unit elemental volume can be expressed as a sheet of elemental volume in two dimensions. ![]() For example, the signed volume of the 3D ellipic cylinder is bounded by surfaces in rectangular form , Imply ![]() An elemental volume ΔV in rectangular form can be defined as Δx times Δy times Δz. Imply ![]() An unit elemental volume can be expressed as ![]() Therefore the unit elemental volume can also be expressed as a sheet of elemental volume of the solid cylinder U along the cartesian coordinate axis x. Imply ![]() Sweeping the unit elemental volume ΔVx along x axis horizontally Since all unit elemental volumes of ΔVx are bounded along x axis, imply ![]() Therefore the volume of the solid cone U is ![]() Link:http://output.to/sideway/default.asp?qno=120600011 Centroid of 3D Body Centroid of 3D BodyThe centroid of 3D Body is determined by the first moment of a three dimensional body with the method of the first moment of volume. ![]() Centroids of VolumesVolume by IntegrationVolume by Triple Integration![]() For example, the signed volume of the 3D region U is bounded by surfaces in rectangular form , Imply ![]() An elemental volume ΔV in rectangular form can be defined as Δx times Δy times Gz. Imply ![]() Therefore the volume of the solid cone U in cartesian coordinates xyz is equal to ![]() In general, the volume of a region can be determined by multiple integration through sweeping the signed elemental volume starting from along any one of the rectangular coordinate axes. Imply Starting from horizontal sweeping along x axis ![]() Considering an elemental volume along x axis. Imply ![]() All elemental volumes can be bounded by curves in the plane yz. And the curves is ![]() Similarly sweeping the elemental volume ΔVyz along y axis horizontally. ![]() Considering an elemental volume ΔVz along y axis. Imply ![]() Since the bounding curves are joined at plane zx, The bounds of the bounding curves are ![]() Therefore the volume of the solid cone U is ![]() The volume of the solid cone U can also be determined starting from other axis. Starting from horizontal sweeping along y axis ![]() Considering an elemental volume along y axis. Imply ![]() All elemental volumes in z direction can be bounded by curves in the plane zx. And the curves is ![]() Similarly sweeping the elemental volume ΔVzx along z axis vertically. ![]() Considering an elemental volume ΔVx along z axis. Imply ![]() The bounding curves in x direction can also be bounded at plane zx. The bounds of the bounding curves are ![]() The volume of the solid cone U can be expressed as ![]() Therefore the volume of the solid cone U is ![]()
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Sideway BICK Blog 18/06 |