WEEK 4
TOPIC: THREE DIMENSIONAL SHAPES
Solid figure are often called 3dimensional shapes. A solid figure is simply anything that occupied space and also has a definite shape.
FACES, EDGES AND VERTICES
FACE: A face is the surface of a solid which is enclosed by edges.
EDGES: An edge of a solid is a line where two faces meet. Note that an edge may be straight or curved
VERTEX: A vertex of a solid is a point or corner where three or more edges meet.
TYPES OF SOLID AND THEIR PROPERTIE
DO THESE
ASSIGNMENT
ASSIGNMENT:
APPLICATION
Surface Area
The surface area of a figure, is the total area of all the sides of the figure.
Triangular Prism(Right Angle Triangle)
To find the surface area of the prism above, follow the steps below.
Step 1: Divide the figure into smaller shapes.
Step 2: Find the area of each smaller shape.
Step 3: Add the areas of each smaller shape.
A right-angle triangle prism can be divided into five smaller shapes; two right angle triangles and three rectangles.
Example
Find the surface area of the prism below.
Pyramid
A pyramid is an object which has: a straight sided shape base (a squared, rectangular, trianglular base etc) and triangular sides which meet at the top (called the apex).
Example
Cylinder
To find the surface area of the cylinder above, follow the steps below.
Step 1: Divide the figure into smaller shapes.
Step 2: Find the area of each smaller shape.
Step 3: Add the areas of each smaller shape.
A cylinder can be divided into three segements: two circles and a curved surface area.
The area of a circle, A = πr2
Since there are two circles in a cylinder, multiply the abover formula by 2, that is:
The area of the circles, A = 2πr2
The curved surface area, C.S.A. = 2πrh
The area of a cylinder, A = Area of the circles + C.S.A.
= 2πr2 + 2πrh
= 2πr (r + h)
Example
Cube
A cube has 6 sides (faces) of the same surface area. Each side (face) of the cube are squares. Recall, the area of a square, A = L2 .
The surface area of a cube, A = 6L2
Where, L is the length of a side of the cube(all the sides of a cube are the same length).
Example
Cuboid
The surface area of a cuboid, A = 2Lw + 2 Lh + 2wh
Where, L is the length of the cuboid
w is the width of the cuboid
And, h is the height of the cuboid.
Example
Sphere
A sphere is a three-dimensional object (such as a ball or the earth) with every point on the surface equidistant (halfway from) from the center.
The surface area of a sphere, A = 4πr2
Where, r is the radius of the sphere.
Example
Surface Area of a sphere, A = 4 πr2
