The Portion of the Curve y=4x Rotated About the X-Axis: Calculating the Volume of the Solid Generated

In mathematics, the process of rotating a curve about an axis is a fundamental concept in calculus, particularly in the study of volumes of solids. When a portion of a curve is rotated about the x-axis, it generates a solid with a specific volume. In this article, we will explore the process of calculating the volume of the solid generated by rotating the portion of the curve y=4x between x=a and x=b about the x-axis.
The problem involves rotating the portion of the curve y=4x between x=a and x=b about the x-axis by 2 radians. This means that the curve will be rotated in a circular motion around the x-axis, generating a solid with a specific volume. The volume of the solid generated is represented by the variable V.
To calculate the volume of the solid generated, we will use the method of disks. This method involves dividing the solid into thin disks, each with a radius equal to the distance from the x-axis to the curve at a given point. The volume of each disk is then calculated and summed up to find the total volume of the solid.
The volume of each disk is given by the formula:
V=πr2Δx
where r is the radius of the disk and Δx is the thickness of the disk.
In this case, the radius of each disk is equal to the distance from the x-axis to the curve at a given point, which is given by the equation y=4x. Therefore, the radius of each disk is 4x.
The thickness of each disk is Δx, which is the difference between the x-coordinates of two consecutive points on the curve.
Substituting these values into the formula, we get:
V=π(4x)2Δx
Simplifying the expression, we get:
V=16πx2Δx
To find the total volume of the solid generated, we need to integrate the expression for the volume of each disk with respect to x.
The limits of integration are a and b, which represent the x-coordinates of the two points on the curve that define the portion of the curve to be rotated.
Therefore, the integral is:
V=16π∫ab​x2Δx
Evaluating the integral, we get:
V=16π[3x3​]ab​
Simplifying the expression, we get:
V=316π​(b3−a3)
In conclusion, the volume of the solid generated by rotating the portion of the curve y=4x between x=a and x=b about the x-axis is given by the expression:
V=316π​(b3−a3)
This expression represents the volume of the solid generated by rotating the portion of the curve about the x-axis.
The final answer is:
V = \frac{16 \pi}{3} (b^3 - a^3)$<br/>
**The Portion of the Curve $y = 4x$ Rotated About the X-Axis: Calculating the Volume of the Solid Generated**

Q: What is the method of disks?
A: The method of disks is a technique used to calculate the volume of a solid generated by rotating a curve about an axis. It involves dividing the solid into thin disks, each with a radius equal to the distance from the axis to the curve at a given point. The volume of each disk is then calculated and summed up to find the total volume of the solid.
Q: How do I calculate the volume of each disk?
A: To calculate the volume of each disk, you need to use the formula:
V=πr2Δx</span></p><p>where<spanclass="katex"><spanclass="katex−mathml"><mathxmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>r</mi></mrow><annotationencoding="application/x−tex">r</annotation></semantics></math></span><spanclass="katex−html"aria−hidden="true"><spanclass="base"><spanclass="strut"style="height:0.4306em;"></span><spanclass="mordmathnormal"style="margin−right:0.02778em;">r</span></span></span></span>istheradiusofthediskand<spanclass="katex"><spanclass="katex−mathml"><mathxmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mimathvariant="normal">Δ</mi><mi>x</mi></mrow><annotationencoding="application/x−tex">Δx</annotation></semantics></math></span><spanclass="katex−html"aria−hidden="true"><spanclass="base"><spanclass="strut"style="height:0.6833em;"></span><spanclass="mord">Δ</span><spanclass="mordmathnormal">x</span></span></span></span>isthethicknessofthedisk.</p><h2><strong>Q:Whatistheradiusofeachdiskinthisproblem?</strong></h2><p>A:Inthisproblem,theradiusofeachdiskisequaltothedistancefromthex−axistothecurveatagivenpoint,whichisgivenbytheequation<spanclass="katex"><spanclass="katex−mathml"><mathxmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>y</mi><mo>=</mo><mn>4</mn><mi>x</mi></mrow><annotationencoding="application/x−tex">y=4x</annotation></semantics></math></span><spanclass="katex−html"aria−hidden="true"><spanclass="base"><spanclass="strut"style="height:0.625em;vertical−align:−0.1944em;"></span><spanclass="mordmathnormal"style="margin−right:0.03588em;">y</span><spanclass="mspace"style="margin−right:0.2778em;"></span><spanclass="mrel">=</span><spanclass="mspace"style="margin−right:0.2778em;"></span></span><spanclass="base"><spanclass="strut"style="height:0.6444em;"></span><spanclass="mord">4</span><spanclass="mordmathnormal">x</span></span></span></span>.Therefore,theradiusofeachdiskis<spanclass="katex"><spanclass="katex−mathml"><mathxmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mn>4</mn><mi>x</mi></mrow><annotationencoding="application/x−tex">4x</annotation></semantics></math></span><spanclass="katex−html"aria−hidden="true"><spanclass="base"><spanclass="strut"style="height:0.6444em;"></span><spanclass="mord">4</span><spanclass="mordmathnormal">x</span></span></span></span>.</p><h2><strong>Q:HowdoIintegratetofindthetotalvolumeofthesolidgenerated?</strong></h2><p>A:Tofindthetotalvolumeofthesolidgenerated,youneedtointegratetheexpressionforthevolumeofeachdiskwithrespectto<spanclass="katex"><spanclass="katex−mathml"><mathxmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>x</mi></mrow><annotationencoding="application/x−tex">x</annotation></semantics></math></span><spanclass="katex−html"aria−hidden="true"><spanclass="base"><spanclass="strut"style="height:0.4306em;"></span><spanclass="mordmathnormal">x</span></span></span></span>.Thelimitsofintegrationare<spanclass="katex"><spanclass="katex−mathml"><mathxmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>a</mi></mrow><annotationencoding="application/x−tex">a</annotation></semantics></math></span><spanclass="katex−html"aria−hidden="true"><spanclass="base"><spanclass="strut"style="height:0.4306em;"></span><spanclass="mordmathnormal">a</span></span></span></span>and<spanclass="katex"><spanclass="katex−mathml"><mathxmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>b</mi></mrow><annotationencoding="application/x−tex">b</annotation></semantics></math></span><spanclass="katex−html"aria−hidden="true"><spanclass="base"><spanclass="strut"style="height:0.6944em;"></span><spanclass="mordmathnormal">b</span></span></span></span>,whichrepresentthex−coordinatesofthetwopointsonthecurvethatdefinetheportionofthecurvetoberotated.</p><h2><strong>Q:Whatisthefinalexpressionforthevolumeofthesolidgenerated?</strong></h2><p>A:Thefinalexpressionforthevolumeofthesolidgeneratedis:</p><pclass=′katex−block′><spanclass="katex−display"><spanclass="katex"><spanclass="katex−mathml"><mathxmlns="http://www.w3.org/1998/Math/MathML"display="block"><semantics><mrow><mi>V</mi><mo>=</mo><mfrac><mrow><mn>16</mn><mi>π</mi></mrow><mn>3</mn></mfrac><mostretchy="false">(</mo><msup><mi>b</mi><mn>3</mn></msup><mo>−</mo><msup><mi>a</mi><mn>3</mn></msup><mostretchy="false">)</mo></mrow><annotationencoding="application/x−tex">V=316π​(b3−a3)</annotation></semantics></math></span><spanclass="katex−html"aria−hidden="true"><spanclass="base"><spanclass="strut"style="height:0.6833em;"></span><spanclass="mordmathnormal"style="margin−right:0.22222em;">V</span><spanclass="mspace"style="margin−right:0.2778em;"></span><spanclass="mrel">=</span><spanclass="mspace"style="margin−right:0.2778em;"></span></span><spanclass="base"><spanclass="strut"style="height:2.0074em;vertical−align:−0.686em;"></span><spanclass="mord"><spanclass="mopennulldelimiter"></span><spanclass="mfrac"><spanclass="vlist−tvlist−t2"><spanclass="vlist−r"><spanclass="vlist"style="height:1.3214em;"><spanstyle="top:−2.314em;"><spanclass="pstrut"style="height:3em;"></span><spanclass="mord"><spanclass="mord">3</span></span></span><spanstyle="top:−3.23em;"><spanclass="pstrut"style="height:3em;"></span><spanclass="frac−line"style="border−bottom−width:0.04em;"></span></span><spanstyle="top:−3.677em;"><spanclass="pstrut"style="height:3em;"></span><spanclass="mord"><spanclass="mord">16</span><spanclass="mordmathnormal"style="margin−right:0.03588em;">π</span></span></span></span><spanclass="vlist−s">​</span></span><spanclass="vlist−r"><spanclass="vlist"style="height:0.686em;"><span></span></span></span></span></span><spanclass="mclosenulldelimiter"></span></span><spanclass="mopen">(</span><spanclass="mord"><spanclass="mordmathnormal">b</span><spanclass="msupsub"><spanclass="vlist−t"><spanclass="vlist−r"><spanclass="vlist"style="height:0.8641em;"><spanstyle="top:−3.113em;margin−right:0.05em;"><spanclass="pstrut"style="height:2.7em;"></span><spanclass="sizingreset−size6size3mtight"><spanclass="mordmtight">3</span></span></span></span></span></span></span></span><spanclass="mspace"style="margin−right:0.2222em;"></span><spanclass="mbin">−</span><spanclass="mspace"style="margin−right:0.2222em;"></span></span><spanclass="base"><spanclass="strut"style="height:1.1141em;vertical−align:−0.25em;"></span><spanclass="mord"><spanclass="mordmathnormal">a</span><spanclass="msupsub"><spanclass="vlist−t"><spanclass="vlist−r"><spanclass="vlist"style="height:0.8641em;"><spanstyle="top:−3.113em;margin−right:0.05em;"><spanclass="pstrut"style="height:2.7em;"></span><spanclass="sizingreset−size6size3mtight"><spanclass="mordmtight">3</span></span></span></span></span></span></span></span><spanclass="mclose">)</span></span></span></span></span></p><h2><strong>Q:Whataretheassumptionsmadeinthisproblem?</strong></h2><p>A:Theassumptionsmadeinthisproblemare:</p><ul><li>Thecurveisrotatedaboutthex−axis.</li><li>Therotationisby<spanclass="katex"><spanclass="katex−mathml"><mathxmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mn>2</mn></mrow><annotationencoding="application/x−tex">2</annotation></semantics></math></span><spanclass="katex−html"aria−hidden="true"><spanclass="base"><spanclass="strut"style="height:0.6444em;"></span><spanclass="mord">2</span></span></span></span>radians.</li><li>Theportionofthecurvetoberotatedisbetween<spanclass="katex"><spanclass="katex−mathml"><mathxmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>x</mi><mo>=</mo><mi>a</mi></mrow><annotationencoding="application/x−tex">x=a</annotation></semantics></math></span><spanclass="katex−html"aria−hidden="true"><spanclass="base"><spanclass="strut"style="height:0.4306em;"></span><spanclass="mordmathnormal">x</span><spanclass="mspace"style="margin−right:0.2778em;"></span><spanclass="mrel">=</span><spanclass="mspace"style="margin−right:0.2778em;"></span></span><spanclass="base"><spanclass="strut"style="height:0.4306em;"></span><spanclass="mordmathnormal">a</span></span></span></span>and<spanclass="katex"><spanclass="katex−mathml"><mathxmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>x</mi><mo>=</mo><mi>b</mi></mrow><annotationencoding="application/x−tex">x=b</annotation></semantics></math></span><spanclass="katex−html"aria−hidden="true"><spanclass="base"><spanclass="strut"style="height:0.4306em;"></span><spanclass="mordmathnormal">x</span><spanclass="mspace"style="margin−right:0.2778em;"></span><spanclass="mrel">=</span><spanclass="mspace"style="margin−right:0.2778em;"></span></span><spanclass="base"><spanclass="strut"style="height:0.6944em;"></span><spanclass="mordmathnormal">b</span></span></span></span>.</li></ul><h2><strong>Q:Whatarethelimitationsofthisproblem?</strong></h2><p>A:Thelimitationsofthisproblemare:</p><ul><li>Theproblemassumesthatthecurveisrotatedaboutthex−axis,whichmaynotbethecaseinallsituations.</li><li>Theproblemassumesthattherotationisby<spanclass="katex"><spanclass="katex−mathml"><mathxmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mn>2</mn></mrow><annotationencoding="application/x−tex">2</annotation></semantics></math></span><spanclass="katex−html"aria−hidden="true"><spanclass="base"><spanclass="strut"style="height:0.6444em;"></span><spanclass="mord">2</span></span></span></span>radians,whichmaynotbethecaseinallsituations.</li><li>Theproblemassumesthattheportionofthecurvetoberotatedisbetween<spanclass="katex"><spanclass="katex−mathml"><mathxmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>x</mi><mo>=</mo><mi>a</mi></mrow><annotationencoding="application/x−tex">x=a</annotation></semantics></math></span><spanclass="katex−html"aria−hidden="true"><spanclass="base"><spanclass="strut"style="height:0.4306em;"></span><spanclass="mordmathnormal">x</span><spanclass="mspace"style="margin−right:0.2778em;"></span><spanclass="mrel">=</span><spanclass="mspace"style="margin−right:0.2778em;"></span></span><spanclass="base"><spanclass="strut"style="height:0.4306em;"></span><spanclass="mordmathnormal">a</span></span></span></span>and<spanclass="katex"><spanclass="katex−mathml"><mathxmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>x</mi><mo>=</mo><mi>b</mi></mrow><annotationencoding="application/x−tex">x=b</annotation></semantics></math></span><spanclass="katex−html"aria−hidden="true"><spanclass="base"><spanclass="strut"style="height:0.4306em;"></span><spanclass="mordmathnormal">x</span><spanclass="mspace"style="margin−right:0.2778em;"></span><spanclass="mrel">=</span><spanclass="mspace"style="margin−right:0.2778em;"></span></span><spanclass="base"><spanclass="strut"style="height:0.6944em;"></span><spanclass="mordmathnormal">b</span></span></span></span>,whichmaynotbethecaseinallsituations.</li></ul><h2><strong>Q:HowcanIapplythisproblemtoreal−worldsituations?</strong></h2><p>A:Thisproblemcanbeappliedtoreal−worldsituationssuchas:</p><ul><li>Calculatingthevolumeofasolidgeneratedbyrotatingacurveaboutanaxis.</li><li>Designingacontaineroravesselwithaspecificvolume.</li><li>Calculatingthevolumeofasolidgeneratedbyrotatingacurveaboutanaxisinathree−dimensionalspace.</li></ul><p>Inconclusion,theproblemofcalculatingthevolumeofthesolidgeneratedbyrotatingtheportionofthecurve<spanclass="katex"><spanclass="katex−mathml"><mathxmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>y</mi><mo>=</mo><mn>4</mn><mi>x</mi></mrow><annotationencoding="application/x−tex">y=4x</annotation></semantics></math></span><spanclass="katex−html"aria−hidden="true"><spanclass="base"><spanclass="strut"style="height:0.625em;vertical−align:−0.1944em;"></span><spanclass="mordmathnormal"style="margin−right:0.03588em;">y</span><spanclass="mspace"style="margin−right:0.2778em;"></span><spanclass="mrel">=</span><spanclass="mspace"style="margin−right:0.2778em;"></span></span><spanclass="base"><spanclass="strut"style="height:0.6444em;"></span><spanclass="mord">4</span><spanclass="mordmathnormal">x</span></span></span></span>between<spanclass="katex"><spanclass="katex−mathml"><mathxmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>x</mi><mo>=</mo><mi>a</mi></mrow><annotationencoding="application/x−tex">x=a</annotation></semantics></math></span><spanclass="katex−html"aria−hidden="true"><spanclass="base"><spanclass="strut"style="height:0.4306em;"></span><spanclass="mordmathnormal">x</span><spanclass="mspace"style="margin−right:0.2778em;"></span><spanclass="mrel">=</span><spanclass="mspace"style="margin−right:0.2778em;"></span></span><spanclass="base"><spanclass="strut"style="height:0.4306em;"></span><spanclass="mordmathnormal">a</span></span></span></span>and<spanclass="katex"><spanclass="katex−mathml"><mathxmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>x</mi><mo>=</mo><mi>b</mi></mrow><annotationencoding="application/x−tex">x=b</annotation></semantics></math></span><spanclass="katex−html"aria−hidden="true"><spanclass="base"><spanclass="strut"style="height:0.4306em;"></span><spanclass="mordmathnormal">x</span><spanclass="mspace"style="margin−right:0.2778em;"></span><spanclass="mrel">=</span><spanclass="mspace"style="margin−right:0.2778em;"></span></span><spanclass="base"><spanclass="strut"style="height:0.6944em;"></span><spanclass="mordmathnormal">b</span></span></span></span>aboutthex−axisisaclassicproblemincalculus.Themethodofdisksisapowerfultechniqueusedtosolvethisproblem,andthefinalexpressionforthevolumeofthesolidgeneratedis:</p><pclass=′katex−block′><spanclass="katex−display"><spanclass="katex"><spanclass="katex−mathml"><mathxmlns="http://www.w3.org/1998/Math/MathML"display="block"><semantics><mrow><mi>V</mi><mo>=</mo><mfrac><mrow><mn>16</mn><mi>π</mi></mrow><mn>3</mn></mfrac><mostretchy="false">(</mo><msup><mi>b</mi><mn>3</mn></msup><mo>−</mo><msup><mi>a</mi><mn>3</mn></msup><mostretchy="false">)</mo></mrow><annotationencoding="application/x−tex">V=316π​(b3−a3)</annotation></semantics></math></span><spanclass="katex−html"aria−hidden="true"><spanclass="base"><spanclass="strut"style="height:0.6833em;"></span><spanclass="mordmathnormal"style="margin−right:0.22222em;">V</span><spanclass="mspace"style="margin−right:0.2778em;"></span><spanclass="mrel">=</span><spanclass="mspace"style="margin−right:0.2778em;"></span></span><spanclass="base"><spanclass="strut"style="height:2.0074em;vertical−align:−0.686em;"></span><spanclass="mord"><spanclass="mopennulldelimiter"></span><spanclass="mfrac"><spanclass="vlist−tvlist−t2"><spanclass="vlist−r"><spanclass="vlist"style="height:1.3214em;"><spanstyle="top:−2.314em;"><spanclass="pstrut"style="height:3em;"></span><spanclass="mord"><spanclass="mord">3</span></span></span><spanstyle="top:−3.23em;"><spanclass="pstrut"style="height:3em;"></span><spanclass="frac−line"style="border−bottom−width:0.04em;"></span></span><spanstyle="top:−3.677em;"><spanclass="pstrut"style="height:3em;"></span><spanclass="mord"><spanclass="mord">16</span><spanclass="mordmathnormal"style="margin−right:0.03588em;">π</span></span></span></span><spanclass="vlist−s">​</span></span><spanclass="vlist−r"><spanclass="vlist"style="height:0.686em;"><span></span></span></span></span></span><spanclass="mclosenulldelimiter"></span></span><spanclass="mopen">(</span><spanclass="mord"><spanclass="mordmathnormal">b</span><spanclass="msupsub"><spanclass="vlist−t"><spanclass="vlist−r"><spanclass="vlist"style="height:0.8641em;"><spanstyle="top:−3.113em;margin−right:0.05em;"><spanclass="pstrut"style="height:2.7em;"></span><spanclass="sizingreset−size6size3mtight"><spanclass="mordmtight">3</span></span></span></span></span></span></span></span><spanclass="mspace"style="margin−right:0.2222em;"></span><spanclass="mbin">−</span><spanclass="mspace"style="margin−right:0.2222em;"></span></span><spanclass="base"><spanclass="strut"style="height:1.1141em;vertical−align:−0.25em;"></span><spanclass="mord"><spanclass="mordmathnormal">a</span><spanclass="msupsub"><spanclass="vlist−t"><spanclass="vlist−r"><spanclass="vlist"style="height:0.8641em;"><spanstyle="top:−3.113em;margin−right:0.05em;"><spanclass="pstrut"style="height:2.7em;"></span><spanclass="sizingreset−size6size3mtight"><spanclass="mordmtight">3</span></span></span></span></span></span></span></span><spanclass="mclose">)</span></span></span></span></span></p><p>Thisproblemcanbeappliedtoreal−worldsituationssuchasdesigningacontaineroravesselwithaspecificvolume,andcalculatingthevolumeofasolidgeneratedbyrotatingacurveaboutanaxisinathree−dimensionalspace.</p>