Visualising Solid Shapes 15.2

Visualising Solid Shapes Full exercise on Visualising Solid Shapes, fully solved. This is a video tutorial for 7th class NCERT CBSE students. For other educational stuff, subscribe and press bell icon. DRAWING SOLIDS ON A FLAT SURFACE Your drawing surface is paper, which is flat. When you draw a solid shape, the images are somewhat distorted to make them appear three-dimensional. It is a visual illusion. You will find here two techniques to help you. Oblique Sketches A picture of a cube, it gives a clear idea of how the cube looks like, when seen from the front. You do not see certain faces. In the drawn picture, the lengths are not equal, as they should be in a cube. Still, you are able to recognise it as a cube. Such a sketch of a solid is called an oblique sketch. How can you draw such sketches? Let us attempt to learn the technique. Step 1 : Draw the front face. Step 2: Draw the opposite face. Sizes of the faces have to be same, but the sketch is somewhat off-set from step 1. Step 3: Join the corresponding corners. Step 4: Redraw using dotted lines for hidden edges. (It is a convention). The sketch is ready now. In the oblique sketch, did you note the following? (i) The sizes of the front faces and its opposite are same; and (ii) The edges, which are all equal in a cube, appear so in the sketch, though the actual measures of edges are not taken so. You could now try to make an oblique sketch of a cuboid (remember the faces in this case are rectangles). Note: You can draw sketches in which measurements also agree with those of a given solid. To do this we need what is known as an isometric sheet. Let us try tomake a cuboid with dimensions 4 cm length, 3 cm breadth and 3 cm height on given isometric sheet. Isometric Sketches Have you seen an isometric dot sheet? (A sample is given at the end of the book). Such a sheet divides the paper into small equilateral triangles made up of dots or lines. To draw sketches in which measurements also agree with those of the solid, we can use isometric dot sheets. Let us attempt to draw an isometric sketch of a cuboid of dimensions 4 × 3 × 3 (which means the edges forming length, breadth and height are 4, 3, 3 units respectively). Step 1: Draw a rectangle to show the front face. Step 2: Draw four parallel line segments of length 3 starting from the four corners of the rectangle. Step 3: Connect the matching corners Step 4: This is an isometric sketch of the cuboid. Note that the measurements are of exact size in an isometric sketch; this is not so in the case of an oblique sketch. EXERCISE 15.2 1. Use isometric dot paper and make an isometric sketch for each one of the given shapes: 2. The dimensions of a cuboid are 5 cm, 3 cm and 2 cm. Draw three different isometric sketches of this cuboid. 3. Three cubes each with 2 cm edge are placed side by side to form a cuboid. Sketch an oblique or isometric sketch of this cuboid. 4. Make an oblique sketch for each one of the given isometric shapes: 5. Give (i) an oblique sketch and (ii) an isometric sketch for each of the following: (a) A cuboid of dimensions 5 cm, 3 cm and 2 cm. (Is your sketch unique?) (b) A cube with an edge 4 cm long. An isometric sheet is attached at the end of the book. You could try to make on it some cubes or cuboids of dimensions specified by your friend. #VisualisingSolidShapes #SolidShapes #NcertSolutions #solvedexercises #teaching #ncert #cbse #maths #MathematicsClassVII #schoolmadeeasy #samrules Make sure to Subscribe and get the latest tutorials for your delight :) http://www.youtube.com/subscription_center?add_user=sumitsumo Make sure to check out our other Video Tutorials! Also, check us out when we're posting other helpful videos all throughout the week to help you tell more and grow more using online video.