Volume of a Section of a Sphere
In this section, we will discuss the volume of a section of a sphere along with solved examples. Let us start with the pre-required knowledge to understand the topic, volume of a section of a sphere. The volume of a three-dimensional object is defined as the space occupied by the object in a three-dimensional space.
What Is Volume of Section of a Sphere?
Volume of section of sphere is defined as the total space occupied by a section of the sphere. A section of a sphere is a portion of a sphere. In other words, it is the shape obtained when the sphere is cut in a specific way. The section of a sphere can have various possible shapes depending on how it is cut. Spherical sector, spherical cap, spherical segment, and spherical wedge are well-known examples of a section of a sphere. Let us see the formulas to calculate volume of these different types of sections of sphere,
- Volume of spherical cap
- Volume of spherical sector
- Volume of spherical segment
- Volume of spherical wedge
Volume of a Spherical Cap Formula
A spherical cap is a portion of a sphere obtained when the sphere is cut by a plane. For a sphere, if the following are given: height h of the spherical cap, radius a of the base circle of the cap, and radius R of the sphere (from which the cap was removed), then its volume can be given by:
Volume of a spherical cap in terms of h and R = (1/3)πh2(3R - h)
By using Pythagoras theorem, (R - h)2 + a2 = R2
Therefore, volume can be rewritten as, Volume of a spherical cap in terms of h and a = (1/6)πh(3a2 + h2)
For a spherical cap having a height equal to the radius, h = R, then it is a hemisphere.
Note: The range of values for the height is 0 ≤ h ≤ 2R and range of values for the radius of the cap is 0 ≤ a ≤ R.
How to Find the Volume of a Spherical Cap?
As we learned in the previous section, the volume of the spherical cap is (1/3)πh2(3R - h) or (1/6)πh(3a2 + h2). Thus, we follow the steps shown below to find the volume of the spherical cap.
- Step 1: Identify the radius of the sphere from which the spherical cap was taken from and name this radius as R.
- Step 2: Identify the radius of the spherical cap and name it as a or the height of the spherical and name it as h.
- Step 3: You can use the relation (R - h)2 + a2 = R2 if any two of the variables are given and the third is unknown.
- Step 4: Find the volume of the spherical cap using the formula, V = (1/3)πh2(3R - h) or V = (1/6)πh(3a2 + h2).
- Step 5: Represent the final answer in cubic units.
Volume of a Spherical Sector (Spherical Cone)
A spherical sector is a portion of a sphere that consists of a spherical cap and a cone with an apex at the center of the sphere and the base of the spherical cap. The volume of a spherical sector can be said as the sum of the volume of the spherical cap and the volume of the cone. For a spherical sector, if the following are given: height h of the spherical cap, radius a of the base circle of the cap, and radius R of the sphere (from which the cap was removed), then its volume can be given by:
Volume of a spherical cone in terms of h and R = (2/3)πR2h
How to Find the Volume of a Spherical Sector (Spherical Cone)?
As we learned in the previous section, the volume of the spherical sector is (2/3) πR2h. Thus, we follow the steps shown below to find the volume of the spherical sector.
- Step 1: Identify the radius of the sphere from which the spherical sector was taken and name this radius as R.
- Step 2: Identify the radius of the spherical cap and name it as a or the height of the spherical cap and name it as h.
- Step 3: You can use the relation (R - h)2 + a2 = R2 if any two of the variables are given and the third is unknown.
- Step 4: Find the volume of the spherical sector using the formula V = (2/3)πR2h.
- Step 5: Represent the final answer in cubic units.
Volume of a Spherical Segment (Spherical Frustum)
A spherical sector is a portion of a sphere that is obtained when a plane cuts the sphere at the top and bottom such that both the cuts are parallel to each other. For a spherical segment, if the following are given: height h of the spherical segment, radius R1 of the base circle of the segment, and radius R2 of the top circle of the segment, then its volume can be given by:
Volume of a spherical segment = (1/6)πh(3R12 + 3R22 + h2)
How To Find the Volume of a Spherical Segment (Spherical Frustum)?
As we learned in the previous section, the volume of the spherical segment is (1/6)πh(3R12 + 3R22 + h2). Thus, we follow the steps shown below to find the volume of the spherical segment.
- Step 1: Identify the radius of the base circle and name this radius as R1 and identify the radius of the top circle and name this radius as R2
- Step 2: Identify the height of the spherical segment and name it as h.
- Step 3: Find the volume of the spherical sector using the formula V = (1/6)πh(3R12 + 3R22 + h2)
- Step 4: Represent the final answer in cubic units.
Volume of a Spherical Wedge
A solid formed by revolving a semicircle about its diameter with less than 360 degrees. For a spherical wedge, if the following are given: angle θ (in radians) formed by the wedge and its radius R, then its volume can be given by:
Volume of a spherical wedge = (θ/2π)(4/3)πR3
If θ is in degrees then volume of a spherical wedge = (θ/360°)(4/3)πR3
How To Find the Volume of a Spherical Wedge?
As we learned in the previous section, the volume of the spherical wedge is (θ/2π)(4/3)πR3. Thus, we follow the steps shown below to find the volume of the spherical wedge.
- Step 1: Identify the radius of the spherical wedge and name it as R.
- Step 2: Identify the angle of the spherical wedge and name it as θ.
- Step 3: Find the volume of the spherical wedge using the formula, V = (θ/2π)(4/3)πR3
- Step 4: Represent the final answer in cubic units.
Solved Examples on Section of a Sphere
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Example 1: Find the volume of a spherical cap having base radius = 7 units and height = 21 units using a section of a sphere formula. (Use π = 22/7)
Solution
Base radius of the spherical cap (a) = 7 units
Height of the spherical cap (h) = 21 units
Volume of the spherical cap = (1/6)πh(3a2 + h2) = (1/6) × (22/7) × 21 × (3 × 72 + 212) = 11 × (3 × 49 + 441) = 6468 units3Answer: Volume of the spherical cap = 6468 units3
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Example 2: Find the volume of the spherical cone if the height of its spherical cap = 7 units and the radius of the original sphere = 9 units. (Use π = 22/7)
Solution
Height of the spherical cap = 7 units
Radius of the original sphere = 9 units
Using section of a sphere formula,
Volume of the spherical cone = (2/3)πR2h = (2/3) × (22/7) × 92 × 7 = 1188 units3Answer: Volume of the spherical cone = 1188 units3
FAQs on the Volume of Section of a Sphere
What Is Meant By Volume of Section of a Sphere?
The total space occupied by a section of the sphere is called the volume of a section of a sphere. A section of a sphere is a portion of a sphere. The volume of a section of a sphere is expressed in square units.
What Is the Volume of Section of a Sphere Formula?
The formulas to calculate the volume of different types of section of a sphere,
- Volume of a spherical cap = (1/3)πh2(3R - h), where, height h of the spherical cap, and radius R of the sphere from which cap was cut.
- Volume of a spherical sector = (2/3)πR2h, where, R is radius of sphere, h is height.
- Volume of a spherical segment = (1/6)πh(3R12 + 3R22 + h2), where, R\(_1\) is base radius, R\(_2\) is radius of top circle, and h is height of spherical segment.
- Volume of a spherical wedge = (θ/2π)(4/3)πR3, where, angle θ (in radians) formed by the wedge and its radius R.
How Do You Find the Volume of a Section of a Sphere?
We can calculate the volume of a section of a sphere using the formula, V = (1/3)πh2(3R - h), where, height h of the spherical section, and radius R of the sphere from which the section was cut.
What Is Volume of a Spherical Cap?
The volume of a spherical cap is given by the formula, Volume of a spherical cap = (1/3)πh2(3R - h), where, height h of the spherical cap, and radius R of the sphere from which cap was cut.
How to Calculate Volume of a Spherical Segment?
The volume of a spherical segment is given by the formula, Volume of a spherical segment = (1/6)πh(3R12 + 3R22 + h2), where, R\(_1\) is base radius, R\(_2\) is radius of top circle, and h is height of spherical segment.
What Is the Volume of Spherical Wedge?
The volume of a spherical wedge is given by the formula, Volume of a spherical wedge = (θ/2π)(4/3)πR3, where, angle θ (in radians) formed by the wedge and its radius R.
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