Title 06-Visualising 3D-Shapes.pdf ✅

6 CHAPTER VISUALISING 3-D SHAPES CONTENTS  2D Shapes (Plane Figures)  3D Shapes (Solids)  Nets  Nets for Building Different 3D Shapes  Drawing Solids on a Flat Surface 2D SHAPES (PLANE FIGURES) The figures which can be described by mentioning two dimensions called length and breadth, are called 2D-shapes or plane figures. Triangles, rectangles, squares, circles etc. can be drawn on paper, these are plane figures. 3D SHAPES (SOLIDS) The shapes like cube, cuboid, cylinder, pyramid etc. which require three dimensions i.e.length, breadth and height or depth are called solid figures or 3-dimensional figures. The objects having definite shape and size are called solids. A solid occupies a fixed amount of space and has three dimensions.  Cuboid It is the shape of a matchbox, a chalk box, a brick, a tile, a book, an almirah etc. It is made of rectangles. Definition : A solid bounded by six rectangular faces (not all equal) is called a cuboid. It has three dimensions, namely length, breadth and height. A B D C E H G F Various parts of a cuboid are 1. Faces : A cuboid has 6 rectangular faces. The opposite faces of a cuboid are identical. In figure ABCD, EFGH, ADHE, BCGF, ABFE, DCGH are faces. 2. Edges : Two adjacent faces of a cuboid meet in a line segment, which is called edge of the cuboid. A cuboid has 12 edges. In figure edges are AB, BC, CD, DA, EF, GH, FG, EH, CG, BF, AE, DH. 3. Vertices : Three edges of a cuboid meet at a point, called a vertex. A cuboid has 8 vertices. In figure 8 vertices are A, B, C, D, E, F, G, H.  Cube It is the shape of sugar lump, dice etc. A cube is made up of square faces. Definition : A cuboid whose length, breadth and height are all equal, is called a cube. Length breadth and height of a cube are equal. A B C D E F G H Various parts of a cube are : 1. Faces : A cube has six square faces. In figure, ABCD, EFGH, ADHE, BCGF, ABFE, DCGH are faces.
2. Edges : A cube has 12 edges. In figure, 12 edges are AB, BC, CD, DA, EF, GH, FG, EH, CG, BF, AE, DH. 3. Vertices : A cube has 8 vertices. 8 vertices are A, B, C, D, E, F, G, H.  Cylinder A solid shape in which top and bottom both are circular while the rest of the surface is curved. It is the shape of a tube light, tin container, circular pillars, circular pipes, circular pencils, measuring jars, road rollers and gas cylinders etc. Curved edge C1 Curved edge C2 F1 Cylinder F2 Flat surface Flat Face Parts of a cylinder 1. A cylinder has no vertex. 2. A cylinder has two curved edges (in figure C1 and C2). 3. A cylinder has one curved face and two flat faces (in figure F1 and F2).  Cone A cone is a solid shape having a plane circular end as the base and whole lateral surface is the curved surface tapering into a point, called the vertex of the cone. Plane surface Curved surface Vertex Parts of a cone : 1. A cone has one vertex. 2. A cone has one curved edge. 3. A cone has one curved face, and one flat face.  Sphere A solid (3-D) shape that has only a curved surface is called sphere. Parts of a sphere 1. A sphere has no vertex. 2. A sphere has no edge. 3. A sphere has a curved surface.  Prism A prism is a solid whose bases are identical polygon faces (triangles, quadrilaterals, pentagons etc.) and the other faces are rectangles. Remember that if the bases of the prism are pentagon, then the prism is known as pentagonal prism. Pentagonal Prism Prism  Triangular Prism A triangular prism is made up of two triangles at each end and three rectangles. A ridge tent is an example of a triangular prism. Triangular prism D F E B C A Parts of triangular prism : 1. It has 6 vertices A, B, C, D, E and F. 2. It has 9 edges. The edges are AB, BC, AC, DE, EF, FD, BD, CF and AE. 3. It has 5 faces. In figure, ABC, DEF, ABDE, AEFC, BDFC are faces.

The following table gives the summary of all above observations : Solid Name No. of Vertices No. of Edges No. of Faces Cuboid 8 12 6 Cube 8 12 6 Cylinder – 2 3 Cone 1 1 2 Sphere – – 1 Triangular Prism 6 9 5 Triangular Pyramid 4 6 4 Square Pyramid 5 8 5 Rectangular Pyramid 5 8 5