Visualising Solid Shapes 15.4

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. Another Way is by Shadow Play A shadow play: Shadows are a good way to illustrate how three-dimensional objects can be viewed in two dimensions. Have you seen a shadow play? It is a form of entertainment using solid articulated figures in front of an illuminated back-drop to create the illusion of moving images. It makes some indirect use of ideas in Mathematics. You will need a source of light and a few solid shapes for this activity. (If you have an overhead projector, place the solid under the lamp and do these investigations.) EXERCISE 15.4 1. A bulb is kept burning just right above the following solids. Name the shape of the shadows obtained in each case. Attempt to give a rough sketch of the shadow. (You may try to experiment first and then answer these questions). A ball, A cylindrical, pipe and A book 2. Here are the shadows of some 3-D objects, when seen under the lamp of an overhead projector. Identify the solid(s) that match each shadow. (There may be multiple answers for these!) A circle, A square, A triangle and A rectangle 3. Examine if the following are true statements: (i) The cube can cast a shadow in the shape of a rectangle. (ii) The cube can cast a shadow in the shape of a hexagon. WHAT HAVE WE DISCUSSED? 1. The circle, the square, the rectangle, the quadrilateral and the triangle are examples of plane figures; the cube, the cuboid, the sphere, the cylinder, the cone and the pyramid are examples of solid shapes. 2. Plane figures are of two-dimensions (2-D) and the solid shapes are of three-dimensions (3-D). 3. The corners of a solid shape are called its vertices; the line segments of its skeleton are its edges; and its flat surfaces are its faces. 4. A net is a skeleton-outline of a solid that can be folded to make it. The same solid can have several types of nets. 5. Solid shapes can be drawn on a flat surface (like paper) realistically. We call this 2-D representation of a 3-D solid. 6. Two types of sketches of a solid are possible: (a) An oblique sketchdoes not have proportional lengths. Still it conveys all important aspects of the appearance of the solid. (b) An isometric sketch is drawn on an isometric dot paper, a sample of which is given at the end of this book. In an isometric sketch of the solid the measurements kept proportional. 7. Visualising solid shapes is a very useful skill. You should be able to see ‘hidden’ parts of the solid shape. 8. Different sections of a solid can be viewed in many ways: (a) One way is to view by cutting or slicing the shape, which would result in the cross-section of the solid. (b) Another way is by observing a 2-D shadow of a 3-D shape. (c) A third way is to look at the shape from different angles; the front-view, the side-view and the top-view can provide a lot of information about the shape observed. # Class7 #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.