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Example Questions
Example Question #3981 : Calculus
Find the volume of the solid obtained by rotating the region bound by   andÂ
 about the y-axis using the Shell Method.Â
The radius of a single shell can be expressed as , the circumference can be expressed asÂ
, and the height can be expressed asÂ
.Â
Â
To obtain the volume of all the shells, we integrate the overall volume.  Our bounds can be found by calculating the endpoints, or where . Thus, our endpoints are atÂ
 andÂ
.
Integrating, we get:Â
Example Question #71 : How To Find Volume Of A Region
Use the Shell Method to find the volume of the solid obtained by rotating the region under the curve  fromÂ
 toÂ
 about the x-axis
.
To use shells we relabel the curve  asÂ
.
The radius of a single shell can be expressed as , the circumference can be expressed asÂ
, and the height can be expressed asÂ
.Â
Â
To obtain the volume of all the shells, we integrate the overall volume.  Our bounds are given as  andÂ
.
Integrating, we get:Â
Â
Example Question #71 : How To Find Volume Of A Region
Use the Shell Method to find the volume of the solid obtained by rotating the region under the curve  fromÂ
 toÂ
 about the x-axis
.
To use shells we relabel the curve  asÂ
.
The radius of a single shell can be expressed as , the circumference can be expressed asÂ
, and the height can be expressed asÂ
.Â
Â
To obtain the volume of all the shells, we integrate the overall volume.  Our bounds are given as  andÂ
.
Integrating, we get:Â
Â
Example Question #3982 : Calculus
Using the method of cross sections, find the volume of the solid bounded by the function
and the x-axis.
The cross sections are squares perpendicular to the x-axis.
The formula for the volume of a solid using the method of cross sections perpendicular to the x-axis on the interval  isÂ
Where  is the area of the cross section.
Because the cross sections are squares with a side length of   the formula becomes
In order to solve the integral we use the inverse power rule which says
 Â
Applying this rule we get
And by the corollary of the Fundamental Theorem of Calculus we get
Example Question #71 : Volume
Determine the volume of the solid obtained by rotating the region bounded by  andÂ
 about the lineÂ
.
To find the endpoints, we set:
and thus, we get y=4 and y=1 as our bounds.
The area can be found by:
Integrating over our volume, we get:
Example Question #71 : Volume
Determine the volume of the solid obtaining by rotating the region bounded by  andÂ
 about the lineÂ
.
To find the bounds, we set . Solving, we getÂ
, giving us bounds ofÂ
 andÂ
.
Â
The cross sectional area is then:
Integrating, we get the volume:
Example Question #71 : How To Find Volume Of A Region
Find the volume of the solid fo revolution formed by rotating the region formed by the x-axis and the graph of  from x=0 to x=1, about the y-axis.
Example Question #72 : How To Find Volume Of A Region
The region enclosed by the curves  andÂ
 is rotated about the x-axis. Using discs or washers, find the volume of the resulting solid.
The intersection points are (0,0) and (1,1). The cross-sectional area is calculated by finding the area between curves, using integration, getting:
The volume is therefore:
Example Question #75 : Volume
The region enclosed by the curves  and
 is rotated about the lineÂ
. Using discs and washers, find the volume of the resulting solid.
The intersection points are (0,0) and (1,1). The cross-sectional area is:
Â
The volume is therefore:
Example Question #72 : Regions
Finding area under a curve is extremely similar to finding the volume.  The volume of a cylinder is .  When finding the volume of a function rotated around the x-axis, we will look at summing infinitesimal cylinders (disks).  The height of each of these cylinders isÂ
, the radius of the cylinder is the function since given any x value, f(x) is the distance from the x-axis to the curve. Â Thus if we want to find the volume of a function f(x) between [a,b] that is rotated about the x-axis we simply use the equationÂ
.
Find the volume of the solid obtained from rotating the function  about the x-axis and bounded by the y-axis and
.
The bounds are  since it is bounded by the y-axis and the line
 and the function isÂ
. Â
Therefore the equation isÂ
. Â
This gives us the answer ofÂ
.
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