Spheres and Spherical Geometry — Worked Examples

These problems progress from whole-sphere calculations to spherical portions and curved-surface geometry. Distinguish the sphere radius RR, circular-section radius rr, and cap or segment height hh.

Example 1: Volume of a sphere

A spherical ball has radius 0.150 m0.150\,\text{m}. Determine its volume.

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Example 2: Radius from sphere surface area

A sphere has total surface area 100π m2100\pi\,\text{m}^2. Determine its radius.

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Example 3: Material volume of a spherical shell

A hollow spherical vessel has outer radius 0.500 m0.500\,\text{m} and inner radius 0.450 m0.450\,\text{m}. Determine the geometric volume of shell material.

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Example 4: Spherical cap volume, curved area, and closed area

A spherical cap is cut from a sphere of radius R=5.00 mR=5.00\,\text{m}. The cap height is h=2.00 mh=2.00\,\text{m}. Determine the cap volume, curved spherical area, base-disk area, and total closed-cap area.

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Example 5: Recover the circular base radius of a cap

A cap is cut from a sphere of radius R=8.00 mR=8.00\,\text{m} and has height h=3.00 mh=3.00\,\text{m}. Determine the radius rr of the circular cutting section.

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Example 6: Spherical segment with two circular bases

A spherical segment of height h=2.00 mh=2.00\,\text{m} has circular base radii a=4.00 ma=4.00\,\text{m} and b=3.00 mb=3.00\,\text{m}. Determine its volume.

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Example 7: Area of a spherical zone

A sphere has radius R=10.0 mR=10.0\,\text{m}. Two parallel planes bound a spherical zone of height h=3.00 mh=3.00\,\text{m}. Determine the zone area.

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Example 8: Volume of a spherical sector

A spherical sector is associated with a zone of height 1.50 m1.50\,\text{m} on a sphere of radius 4.00 m4.00\,\text{m}. Determine the sector volume.

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Example 9: Spherical lune and wedge

Two great-circle planes on a sphere of radius 6.00 m6.00\,\text{m} meet at angle 30.0∘30.0^\circ. Determine the area of the spherical lune and the volume of the corresponding wedge.

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Example 10: Area of a spherical triangle

A spherical triangle lies on a sphere of radius 10.0 m10.0\,\text{m} and has interior angles 100∘100^\circ, 110∘110^\circ, and 120∘120^\circ. Determine its area.

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Example 11: Great-circle arc length

For a spherical Earth approximation with radius R=6371 kmR=6371\,\text{km}, two points subtend a central angle of 12.0∘12.0^\circ. Estimate their great-circle arc distance.

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Example 12: Recasting a cylinder into a sphere

A solid metal cylinder of radius 6.00 cm6.00\,\text{cm} and height 8.00 cm8.00\,\text{cm} is melted and recast into one sphere with no material loss. Determine the sphere radius.

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Spherical-geometry calculation check

Keep angular units explicit. Formulas such as Alune=2R2θA_{\text{lune}}=2R^2\theta require θ\theta in radians, while a spherical-excess formula written with the factor π/180∘\pi/180^\circ accepts degrees. For caps and segments, do not confuse the sphere radius with the radius of the cutting circle, and state whether an area answer is curved-only or includes flat cut faces.