Geometry Surface Area and Volume of Spheres October 18, 2015 Goals Find the surface area of spheres....
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Transcript of Geometry Surface Area and Volume of Spheres October 18, 2015 Goals Find the surface area of spheres....
Geometry
Surface Area and Volume of Spheres
April 20, 2023
Goals
Find the surface area of spheres. Find the volume of spheres. Solve problems using area and volume.
April 20, 2023
Sphere
radius
Great Circle
(Divides the sphere into two halves.)
Sphere Demo
The set of points in space that are equidistant from the same point, the center.
April 20, 2023
Hemisphere
r
Half of a sphere.
April 20, 2023
Sphere Formulas
r
2
343
4SA r
V r
April 20, 2023
Using a Calculator
You may find it easier to use the formula for volume in this form:
343rV
April 20, 2023
Example
2
2
2
343
343
323
4
4 2
16
50.3
2
33.5
SA r
V r
Find the Surface Area and the Volume of a sphere with a radius of 2.
April 20, 2023
Your Turn Find the surface area and volume.
7 in.
2
343
4 7
196
615.8
7
1372
31436.8
SA
V
April 20, 2023
Problem 1
A snowman is made with three spheres. The largest has a diameter of 24 inches, the next largest has a diameter of 20 inches, and the smallest has a diameter of 16 inches. Find the volume of the snowman.
April 20, 2023
Problem 1 Solution
A snowman is made with three spheres. The largest has a diameter of 24 inches, the next largest has a diameter of 20 inches, and the smallest has a diameter of 16 inches. Find the volume of the snowman.
The radii are 12 in, 10 in, and 8 in.
April 20, 2023
Problem 1 Solution
The radii are 12 in, 10 in, and 8 in.
343
343
343
8 2144.66
10 4188.79
12 7238.23
V
V
V
13,571.68 cu in
April 20, 2023
Or, for easier calculation…
3 3 34 4 43 3 3
3 3 343
43
(8 ) (10 ) (12 )
(8 10 12 )
(3240)
13,571.68
V
April 20, 2023
Problem 2This is a grain silo, as found on many farms. They are used to store feed grain and other materials. They are usually cylindrical with a hemispherical top.
Assume that the concrete part has a height of 50 feet, and the diameter of the cylinder is 18 feet.
Find the volume of the silo.
April 20, 2023
Problem 2 Solution
50
18 Volume of Cylinder
V = r2h
V = (92)(50)
V = 81 50
V = 4050
V 12723.5 cu. ft.
9
April 20, 2023
Problem 2 SolutionVolume of Hemisphere
343 9
972
3053.6 cu. ft.
V
50
18
9This is the volume of a sphere. The volume of the hemisphere is half of this value, which is 1526.8 cu. ft.
April 20, 2023
Problem 2 SolutionVolume of Cylinder
12723.5
Volume of Hemisphere
1526.8
Total Volume
12723.5 + 1526.8 = 14250.3 cu. ft.
50
18
9
April 20, 2023
Problem 2 ExtensionTotal Volume =14250.3 cu. ft.
One bushel contains 1.244 cubic feet. How many
bushels are in the silo?
14250.3 1.244 =
11455.2 bushels
April 20, 2023
Problem 3A sphere is inscribed inside a cube which measures 6 in. on a side. What is the ratio of the volume of the sphere to the volume of the cube?
Skip
April 20, 2023
Problem 3 Solution
6
6
6
Volume of the Cube:
6 6 6 = 216 cu in
Radius of the Sphere:
3 in.
Volume of the Sphere:3
343
43
3
(27)
36
V
April 20, 2023
Problem 3 Solution
6
6
6
Volume of the Cube:
216 cu in
Volume of the Sphere:
36
Ratio of Volume of Sphere to Volume of Cube3
36 36
216 36 6 6
April 20, 2023
Problem 4A mad scientist makes a potionin a full spherical flask which has a diameter of 4 inches. To drink it, he pours it into a cylindrical cup with a diameter of 3.5 inches and is 3.5 inches high. Will the potion fit into the cup? If not, how much is left in the flask?
Skip
April 20, 2023
Problem 4 Solution
Flask Volume:
Diameter = 4 inches
Radius = 2 inches
343 2
4 8
333.5 cu in
V
April 20, 2023
Problem 4 Solution
Cup Volume:
Diameter = 3.5 inches
Radius = 1.75 inches
Height = 3.5 inches
2(1.75 )(3.5)
33.7 cu in
V
33.5 cu in
April 20, 2023
Problem 4 Solution
The flask holds 33.5 cu in.
The cup holds 33.7 cu in.
Yes, the potion fits into the cup.
33.5 cu in
33.7 cu in
April 20, 2023
Problem 5
The surface area of a sphere is 300 cm2.
Find:
1. Its radius,
2. The circumference of a great circle,
3. Its volume.
Skip
April 20, 2023
Problem 5 Solutions2
2
2
4
300 4
300 23.874
4
2
. 9
7
8
3.8
SA r
r
r
r
r
343
343
2
30.72
489.
2 (4.89)
.
8
(4 89 )
C r
V r
April 20, 2023
Summary
A sphere is the set of points in space equidistant from a center.
A hemisphere is half of a sphere. A great circle is the largest circle that can
be drawn on a sphere. The diameter of a great circle equals the diameter of the sphere.
April 20, 2023
Formulas to Know
r
2
343
4SA r
V r
April 20, 2023
Last ProblemOn a far off planet, Zenu was examining his next target, Earth. The radius of the Earth is 3963 miles. What is the volume of material that will be blown into space?
Skip
April 20, 2023
Last Problem Solution
343
11
3963
2.607 10 cubic miles
260,711,883,000 cu mi
V
April 20, 2023
Practice Problems