Formula for the Volume of a Cylinder and a Hemisphere

Oct 13, 2025 by pinkandtrash.com 112 views

Introduction

In this problem, we are given a room in the form of a cylinder surmounted by a hemispherical dome. The base radius of the hemisphere is half of the height of the cylindrical part. We are asked to find the height of the cylindrical part if the room contains 1408/21 m³ of air. To solve this problem, we will use the formula for the volume of a cylinder and a hemisphere.

Formula for the Volume of a Cylinder and a Hemisphere

The formula for the volume of a cylinder is given by:

V = πr²h

where V is the volume, π is a constant approximately equal to 22/7, r is the radius of the base, and h is the height of the cylinder.

The formula for the volume of a hemisphere is given by:

V = (2/3)πr³

where V is the volume, π is a constant approximately equal to 22/7, and r is the radius of the hemisphere.

Given Information

We are given that the room contains 1408/21 m³ of air. Let's assume that the height of the cylindrical part is h meters. Then, the radius of the base of the cylinder is also h/2 meters, since the base radius of the hemisphere is half of the height of the cylindrical part.

Volume of the Cylindrical Part

The volume of the cylindrical part is given by:

V_cylinder = π(h/2)²h

Simplifying the expression, we get:

V_cylinder = (πh³)/4

Volume of the Hemispherical Dome

The volume of the hemispherical dome is given by:

V_hemisphere = (2/3)π(h/2)³

Simplifying the expression, we get:

V_hemisphere = (πh³)/12

Total Volume of the Room

The total volume of the room is the sum of the volumes of the cylindrical part and the hemispherical dome. We are given that the total volume is 1408/21 m³. Therefore, we can write:

V_cylinder + V_hemisphere = 1408/21

Substituting the expressions for V_cylinder and V_hemisphere, we get:

((πh³)/4) + ((πh³)/12) = 1408/21

Solving for h

To solve for h, we can simplify the equation by combining the terms:

(3πh³)/12 + (πh³)/12 = 1408/21

Combine like terms:

(4πh³)/12 = 1408/21

Multiply both sides by 12:

4πh³ = (1408/21) × 12

Simplify the right-hand side:

4πh³ = 768

Divide both sides by 4π:

h³ = 192/π

Take the cube root of both sides:

h = ∛(192/π)

Calculating the Value of h

Now, we can calculate the value of h using the approximate value of π as 22/7.

h = ∛(192/(22/7))

h = ∛(192 × 7/22)

h = ∛(672/22)

h = ∛(30.545)

h ≈ 3.1

Conclusion

In this problem, we were given a room in the form of a cylinder surmounted by a hemispherical dome. We were asked to find the height of the cylindrical part if the room contains 1408/21 m³ of air. Using the formula for the volume of a cylinder and a hemisphere, we were able to solve for the height of the cylindrical part. The value of h is approximately 3.1 meters.

Discussion

This problem requires a good understanding of the formulas for the volume of a cylinder and a hemisphere. It also requires the ability to simplify complex expressions and solve for a variable. The problem is a good example of how to use mathematical formulas to solve real-world problems.

Key Concepts

Formula for the volume of a cylinder
Formula for the volume of a hemisphere
Simplifying complex expressions
Solving for a variable

Practice Problems

A room is in the form of a sphere. If the room contains 1408/21 m³ of air, find the radius of the sphere.
A cylinder has a height of 10 meters and a radius of 5 meters. Find the volume of the cylinder.
A hemisphere has a radius of 5 meters. Find the volume of the hemisphere.

Solutions

Let's assume that the radius of the sphere is r meters. Then, the volume of the sphere is given by:

V = (4/3)πr³

We are given that the volume of the sphere is 1408/21 m³. Therefore, we can write:

(4/3)πr³ = 1408/21

Solving for r, we get:

r ≈ 3.1

The volume of the cylinder is given by:

V = πr²h

Substituting the values, we get:

V = π(5)²(10)

V = 785 m³

The volume of the hemisphere is given by:

V = (2/3)πr³

Substituting the value, we get:

V = (2/3)π(5)³

V = 523.6 m³

Introduction

In our previous article, we discussed a problem where a room is in the form of a cylinder surmounted by a hemispherical dome. We were given that the base radius of the hemisphere is half of the height of the cylindrical part and that the room contains 1408/21 m³ of air. We were asked to find the height of the cylindrical part. In this article, we will answer some frequently asked questions related to this problem.

Q: What is the formula for the volume of a cylinder and a hemisphere?

A: The formula for the volume of a cylinder is given by:

V = πr²h

where V is the volume, π is a constant approximately equal to 22/7, r is the radius of the base, and h is the height of the cylinder.

The formula for the volume of a hemisphere is given by:

V = (2/3)πr³

where V is the volume, π is a constant approximately equal to 22/7, and r is the radius of the hemisphere.

Q: How do I simplify complex expressions in this problem?

A: To simplify complex expressions, you can use the following steps:

Combine like terms
Use the distributive property
Use the associative property
Use the commutative property

For example, in the problem, we had the expression:

((πh³)/4) + ((πh³)/12)

We can simplify this expression by combining the terms:

(3πh³)/12 + (πh³)/12

Combine like terms:

(4πh³)/12

Q: How do I solve for a variable in this problem?

A: To solve for a variable, you can use the following steps:

Isolate the variable
Use inverse operations
Simplify the expression

For example, in the problem, we had the equation:

(4πh³)/12 = 768

We can solve for h by multiplying both sides by 12:

4πh³ = 768 × 12

Simplify the right-hand side:

4πh³ = 9216

Divide both sides by 4π:

h³ = 9216/4π

Take the cube root of both sides:

h = ∛(9216/4π)

Q: What is the value of h in this problem?

A: The value of h is approximately 3.1 meters.

Q: How do I calculate the value of h using the approximate value of π as 22/7?

A: To calculate the value of h, you can use the following steps:

Substitute the approximate value of π as 22/7 into the expression for h
Simplify the expression
Take the cube root of both sides

For example, in the problem, we had the expression:

h = ∛(192/π)

Substitute the approximate value of π as 22/7:

h = ∛(192/(22/7))

h = ∛(192 × 7/22)

h = ∛(672/22)

h = ∛(30.545)

h ≈ 3.1

Q: What are some common mistakes to avoid in this problem?

A: Some common mistakes to avoid in this problem include:

Not simplifying complex expressions
Not solving for the variable correctly
Not using the correct formula for the volume of a cylinder and a hemisphere
Not checking the units of the answer

Q: What are some real-world applications of this problem?

A: Some real-world applications of this problem include:

Architecture: The problem can be used to calculate the volume of a room in a building.
Engineering: The problem can be used to calculate the volume of a container or a tank.
Science: The problem can be used to calculate the volume of a sphere or a hemisphere in a scientific experiment.

Q: How can I practice solving problems like this?

A: To practice solving problems like this, you can try the following:

Practice simplifying complex expressions
Practice solving for variables
Practice using the formula for the volume of a cylinder and a hemisphere
Practice checking the units of the answer

You can also try solving problems like this on your own or with a friend.