Name: Surface Area of a Sphere and a Hemisphere-Demonstration | 视频 | 干净世界
Uploaded: 2023-12-01T23:22:05.402Z
Duration: 2 min 3 s
Description: In this video, you will watch a demonstration of the surface area of a sphere and a hemisphere. Why is the formula for surface area of a sphere 4πr^2? If you cu... | 视频 | 干净世界

MooMooMath and Science

https://video1-us-east.cloudokyo.cloud/video/v6/37/31/29/373129e5-3312-4d17-a8b0-4a32f7a62fb2/master.m3u8

In this video, you will watch a demonstration of the surface area of a sphere and a hemisphere.
Why is the formula for surface area of a sphere 4πr^2?
If you cut a sphere exactly in half the flat surface creates the great circle of the sphere.
The formula for the area of a circle is πr^2
The ratio of the area of a great circle to total surface area of the sphere is 4:1
You can calculate the ratio with this example
Radius of the sphere is 3 cm
Formula for area of a circle equals = πr^2
3.14 * 3^2 = 28.26
Formula for surface area equals 4 πr^2
4 * 3.14 * 3^2 = 113.04
113.04/28.26 = 4
Try it with any radius
Now let’s look at a hemisphere
A hemisphere is sphere cut exactly in half.
The ratio of the area of the great circle to the surface area of the hemisphere is 3:1 if you include the flat surface
Let’s work an example
Radius of the hemisphere equals 2 cm
Area = 3.14*2^2 = 12.56
Surface area of the hemisphere = 3 * 3.14 * 2^2 = 37.68
37.68/12.56 = 3
Now let’s see it visually
I covered a sphere and a hemisphere in aluminum foil.

Check out: Find volume of a sphere
https://www.youtube.com/watch?v=rUjl7VN9nxE

Please watch: "Study Skills Teacher's Secret Guide to your Best Grades" 
https://www.youtube.com/watch?v=f3bsg8gaSbw
-~-~~-~~~-~~-~-