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Water in a bowl A hemispherical bowl of radius 8 inches is filled to a depth of \(h\) inches, where \(0 \leq h \leq 8 .\) Find the volume of water in the bowl as a function of \(h\). (Check the special cases \(h=0 \text { and } h=8 .)\)

Short Answer

Expert verified
Answer: The volume of the water in the bowl, as a function of the depth h, can be expressed as: \(V_\text{water} = \pi (8)^2 h - \frac{1}{3} \pi (64h - h^2)(8 - h)\).

Step by step solution

01

Determine the volume of the water as a cylinder

The volume of a cylinder is calculated using the formula \(V_\text{cylinder} = \pi r_\text{cylinder}^2 h\). In this case, the radius of the cylinder is equal to the radius of the bowl, 8 inches, and the height is equal to the depth of the water, h inches. Thus, we have: \(V_\text{cylinder} = \pi (8)^2 h\)
02

Determine the volume of the spherical cap above the water level

To find the volume of the spherical cap, we need to find the height and radius of the cap. We can use the Pythagorean theorem to relate the bowl's radius (8 inches) to the height and radius of the cap. Suppose the height of the cap is \(h_\text{cap}\) inches and its radius is \(r_\text{cap}\) inches. Then, \(h_\text{cap}^2 + r_\text{cap}^2 = 8^2\), and \(h_\text{cap} = \sqrt{8^2 - r_\text{cap}^2}\) Now, since the height of the cylindrical water is h inches, we can relate \(h_\text{cap}\) to h: \(h + h_\text{cap} = 8\) Substituting for \(h_\text{cap}\), we get: \(h + \sqrt{8^2 - r_\text{cap}^2} = 8\) Solving for \(r_\text{cap}\), we obtain: \(r_\text{cap}^2 = 8^2 - (8 - h)^2\) \(r_\text{cap}^2 = 64h - h^2\) The volume of the spherical cap is given by the formula \(V_\text{cap} = \frac{1}{3} \pi r_\text{cap}^2 h_\text{cap}\). Substituting the expressions for \(r_\text{cap}^2\) and \(h_\text{cap}\), we get: \(V_\text{cap} = \frac{1}{3} \pi (64h - h^2)(8 - h)\)
03

Determine the volume of the water in the bowl

The volume of the water in the bowl can be found by subtracting the volume of the spherical cap above the water level from the total volume of the cylindrical water. Therefore: \(V_\text{water} = V_\text{cylinder} - V_\text{cap}\) \(V_\text{water} = \pi (8)^2 h - \frac{1}{3} \pi (64h - h^2)(8 - h)\) This is our desired expression for the volume of the water in the bowl as a function of h.
04

Check the special cases \(h = 0\) and \(h = 8\)

When we have no water in the bowl (\(h = 0\)), the volume of the water, according to our function, should be 0: \(V_\text{water} = \pi (8)^2 (0) - \frac{1}{3} \pi (64(0) - (0)^2)(8 - 0)\) \(V_\text{water} = 0\) Thus, our function works for \(h = 0\). When the bowl is completely filled with water (\(h = 8\)), the volume, according to our function, should be equal to the volume of the hemisphere: \(V_\text{water} = \pi (8)^2 (8) - \frac{1}{3} \pi (64(8) - (8)^2)(8 - 8)\) \(V_\text{water} = \pi (8)^2 (8) - 0\) \(V_\text{water} = \frac{2}{3} \pi (8)^3\) This is equal to the volume of the hemisphere, so our function works for \(h = 8\) as well.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Spherical Cap Volume
Understanding the volume of a spherical cap is essential when dealing with partial volumes in spherical objects, such as a bowl partially filled with water. A spherical cap is the portion of a sphere that lies above or below a plane cutting through it.

In geometric terms, the volume of a spherical cap can be defined using the formula \(V_\text{cap} = \frac{1}{3} \pi h^2 (3R - h)\), where \(R\) is the radius of the sphere, and \(h\) is the height of the cap from the plane of intersection to the top of the cap. This formula encapsulates the relationship between the height and the curved surface area of the cap.

When calculating this volume in the context of a bowl filled with water, we can envision the empty part of the hemisphere as a spherical cap and use the formula above to determine its volume, thereby helping us find the volume occupied by the water by subtracting this from the full volume of the hemisphere.
Volume of a Cylinder
The concept of the volume of a cylinder is often used in tandem with other geometric formulas to solve complex problems. A cylinder is a three-dimensional shape with two parallel circular bases connected by a curved surface. The volume \(V\) of the cylinder is the amount of space contained within it and can be calculated with the familiar formula \(V = \pi r^2 h\), where \(r\) is the radius of the base circle and \(h\) is the height of the cylinder.

For the hemispherical bowl exercise, this calculation serves as the initial step to finding the volume of water by treating the water as if it were contained within a cylindrical volume before adjustments for the spherical shape are made.
Integrals in Geometry
The use of integrals in geometry allows us to calculate areas, volumes, and other properties involving curves and shapes. Integration is a concept from calculus that helps in finding the sum of infinite infinitesimal quantities. In terms of volume, integration can be applied to find the volume of irregular shapes by adding up the infinite number of infinitesimally thin disks or slices that make up the shape.

The process often involves establishing a function that provides the cross-sectional area of a figure at a given position and then integrating this function over a specific interval. For the spherical bowl, integration principles are applied in a more abstract manner through the derivation of the volume formulas for spheres and spherical caps.
Pythagorean Theorem
The Pythagorean theorem is one of the most recognized principles in geometry, expressing a fundamental relation in Euclidean geometry among the three sides of a right triangle. It states that the square of the length of the hypotenuse \(c\) is equal to the sum of the squares of the other two sides' lengths (\(a\) and \(b\)):

\(c^2 = a^2 + b^2\)

The theorem is not only useful in simple right-angle triangle calculations but also serves as a powerful tool in a wide array of geometric problems. In the context of finding the volume of water in a hemispherical bowl, the Pythagorean theorem helps determine the relationship between the radius of the bowl, the height of the water, and the radius of the spherical cap. By applying the theorem, we can solve for unknown quantities and eventually find the volume of water in the bowl.

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Most popular questions from this chapter

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