7th Class Mathematics Visualising Solid Shapes

 Visualising Solid Shapes

• Description of Some Basic Shapes:

            (i) Square

It has four sides and four corners.      

            All its sides are of the same length.

            (ii) Rectangle

It has four sides and four corners.                  

            The opposite sides of a rectangle are of the same length.

            (iii) Triangle

            It has three sides and three vertices.                                                        

            (iv) Cuboid 

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

            (v) Cube

(vi) Cylinder

It has 3 faces

                               \[\to\]

            1 curved face and 2 flat faces.

            It has 2 curved edges.

            (vii) Cone

It has 2 faces

                               \[\to\]

            1 curved face and

            It has 1 curved edge.

• Three dimensional shapes have length, breadth and height or depth.
• Two-dimensional shapes have only length and breadth.
• Three-dimensional (or 3 - D) shapes can be visualised 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. Some dice have number, 1 to 6 on their faces.
• A solid can be sketched in two ways.
• An oblique sketch which does not have proportional lengths, but conveys all important aspects of the appearance of the solid.
• 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:
• Slicing the shape results in the cross-section of the solid.
• Observing a 2-D shadow of a 3-D shape.
• Looking at the shape from different angles, i.e., the front-view, the side-view and the top-view.

• Description of few more solid shapes