7th Class Mathematics Visualising Solid Shapes Solid Shapes

SOLID SHAPES

FUNDAMENTALS               

•           Description of Some basic shapes:

(a) Square

It has four sides and four comers, All its sides are of the same length.

(b) Rectangle.

It has four sides and four comers. The opposite sides of a rectangle are parallel and of the same length. Every interior angle is a right \[\angle le\].

(c) Triangle

It has three sides and three vertices.

(d) Cuboid

It has 6 flat faces, 12 straight edges and 8 vertices.

(e) Cube

It has 6 flat faces, 8 vertices and 12 straight edges.

(f) Cylinder

It has 3 faces s\[\to \]1 curved face and 2 flat faces.

(g) Cone

It has 2 faces \[\to \] 1 curved face and 1 flat face.

It has 1 curved edge.

•          Two- dimensional shapes have only length and breadth.
•         Three dimensional shapes have length, breadth and height or depth.
•         Three-dimensional (or 3-D) shapes can be visualized on a two dimensional (or 2-D) surface.
•          A net is a skeleton-outline in 2-D, which when folded results in a 3-D shape. The same solid can have several types of nets.
•          Dice are cubes with dots on each face: Opposite faces of a die always have a total of seven dots on them. Generally, dice have number, 1 to 6 on their faces.
•         A solid can be sketched in two ways.

(a) An oblique sketch which does not have proportional faces but gives a realistic feel of the 3-D solid.

e.g.. Oblique sketch of a cuboid.

(b) An isometric sketch, drawn on an isometric dot paper, which has proportional measurements of the solid.

•          Different sections of a solid can be viewed in many ways:

(a) Slicing the shape results in the cross - section of the solid.

(b) Observing a 2 - D shadow of a 3 - D shape.

(c) Looking at the shape from different angles, i.e., the front-view, the side-view and the top-view.

Front and top view of a cylinder

•          Description of few more solid shapes