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6.2.6 - Hemisphere

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Curved Surface Area

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Teacher
Teacher

Today, we will start with the hemisphere's Curved Surface Area. Can anyone tell me the formula for the Curved Surface Area of a hemisphere?

Student 1
Student 1

Is it `CSA = 2πr²`?

Teacher
Teacher

That's correct! CSA stands for Curved Surface Area. The formula shows that the surface area depends solely on the radius. Remember this with the mnemonic: **'2π for Curved hemisphere'**.

Student 2
Student 2

Why is it multiplied by 2?

Teacher
Teacher

Good question! The factor of 2 accounts for the fact that the area involves half of a full sphere’s surface area. Remember to visualize it!

Total Surface Area

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Teacher
Teacher

Now let's talk about Total Surface Area. Does anyone remember the formula?

Student 3
Student 3

Is it `TSA = 3πr²`?

Teacher
Teacher

Exactly! The Total Surface Area includes the curved surface area plus the area of the base which is a circle. It's all about combining different areas!

Student 4
Student 4

How do we find the area of the base?

Teacher
Teacher

The area of the base is simply `πr²`, and that's why you add it to the CSA to get TSA. Try simplifying it as: **'3 parts of π for Total'**.

Volume

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Teacher
Teacher

Finally, who can tell me the volume of a hemisphere?

Student 1
Student 1

I think it's `Volume = (2/3)πr³`.

Teacher
Teacher

Spot on! This formula tells us how much space is contained within the hemisphere. Remember, the `r³` suggests that volume grows cubically with radius.

Student 2
Student 2

What’s the significance of the fraction 2/3?

Teacher
Teacher

The fraction indicates that a hemisphere is two-thirds of the volume of a full sphere, hence we divide the entire volume of a sphere, which is `4/3πr³`, by 2.

Introduction & Overview

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Quick Overview

This section focuses on the measurement of surface area and volume of a hemisphere, including formulas for curved surface area, total surface area, and volume.

Standard

The hemisphere is a three-dimensional shape where the formulas for its surface area and volume are derived and explained. The major components covered include the curved surface area (CSA), total surface area (TSA), and volume, each with specific formulas and applications.

Detailed

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Audio Book

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Curved Surface Area (CSA) of a Hemisphere

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● Curved Surface Area (CSA) = 2πr²

Detailed Explanation

The Curved Surface Area (CSA) of a hemisphere is calculated using the formula CSA = 2πr², where 'r' is the radius of the hemisphere. This formula gives the area of the curved part of the hemisphere, excluding the flat circular base. It basically tells us how much surface area is present on the outside of the hemispherical shape.

Examples & Analogies

Imagine a bowl that is shaped like a half-sphere. The curved surface area would be the outer area of the bowl that you can touch, while the base where the bowl sits flat on the table is not included in this calculation.

Total Surface Area (TSA) of a Hemisphere

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● Total Surface Area (TSA) = 3πr²

Detailed Explanation

The Total Surface Area (TSA) of a hemisphere includes both the curved surface area and the area of the flat circular base. The formula for TSA is TSA = 3πr². Here, the 2πr² represents the curved surface area, and πr² represents the area of the base. Therefore, we add these two areas together to get the total surface area of the hemisphere.

Examples & Analogies

Continuing with the bowl analogy, if you want to paint the entire outside of the bowl and cover the bottom as well, you'd need to calculate the total surface area, which includes both the curved surface and the flat base.

Volume of a Hemisphere

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● Volume = \frac{2}{3} πr³

Detailed Explanation

The volume of a hemisphere is given by the formula Volume = (2/3)πr³, where 'r' represents the radius. This formula calculates how much space is available inside the hemisphere. It's derived from the volume formula of a full sphere, which is (4/3)πr³, and since a hemisphere is half of a sphere, we take half of that volume, which further simplifies to (2/3)πr³.

Examples & Analogies

Think of the inside of an ice cream scoop that is shaped like a hemisphere. The volume would tell you how much ice cream can fit inside before it starts overflowing.

Definitions & Key Concepts

Learn essential terms and foundational ideas that form the basis of the topic.

Key Concepts

  • Curved Surface Area (CSA): The formula for CSA of a hemisphere is 2πr².

  • Total Surface Area (TSA): The formula for TSA is 3πr², which includes the base area.

  • Volume: The volume of a hemisphere is expressed as (2/3)πr³, representing the space it occupies.

Examples & Real-Life Applications

See how the concepts apply in real-world scenarios to understand their practical implications.

Examples

  • Example 1: Calculate the TSA of a hemisphere with radius 3 cm.

  • Example 2: Find the volume of a hemisphere with a radius of 5 cm.

Memory Aids

Use mnemonics, acronyms, or visual cues to help remember key information more easily.

🎵 Rhymes Time

  • Two pi r squared, for the curved flair, three pi r squared, for total care.

📖 Fascinating Stories

  • Once there was a half-sphere, it loved to measure its roundness. It counted its curved area using 2 times pi times radius squared, feeling very proud, while for the total area, it remembered to add a flat base.

🧠 Other Memory Gems

  • To remember CSA = 2πr²: Think of 2 Pictures of Radiant Roses.

🎯 Super Acronyms

TSA = Total Surface Area

  • Think T.S.A. = Total Shapes adding.

Flash Cards

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Glossary of Terms

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  • Term: Hemisphere

    Definition:

    Half of a sphere, divided by a plane passing through its center.

  • Term: Curved Surface Area (CSA)

    Definition:

    The area of the curved portion of a solid figure, ignoring any bases.

  • Term: Total Surface Area (TSA)

    Definition:

    The sum of the areas of all surfaces of a solid figure, including bases.

  • Term: Volume

    Definition:

    The amount of space an object occupies, measured in cubic units.