 Hello everyone, this is Shila Ratnabanswade from Valchan Institute of Technology, Solar Port. Today we are going to see the topic sections of solids and in that we will see the sub-point as introduction to sections of solids, learning outcome. At the end of this session, the students will be able to discuss the types of section plane. I suggest you to pause the video at this moment and recall the basics of orthographic projection that is the principal planes and the section view that you have studied in orthographic projection. As we all know, solids are 3D objects which have definite length, breadth and height. So they have edges, they have corners. Curves are either bounded by a plane surface or a curved surface or a combination of both. Plane surface can be seen in prisms and pyramids whereas curved surface can be seen in cones and cylinders. Solids are classified under two main headings, first the polyhedron. For example, an hexagonal prism, as you can see polyhedrons have two types, one can be the pyramid and one can be the prism. What you are seeing is an hexagonal prism which has a bottom base, a top base where three edges coincide, they form a corner. So this is the vertical edge or the longer edge and this is only base or bottom base. So as this being a hexagonal prism, the base is in hexagonal fashion as well as the top base is also in hexagonal fashion. This central line or the line joining center of top base and the bottom base is called as axis of the solid. So this is an example of a polyhedron and in that particular it is a prism. Further moving on to solids of revolution, solids of revolution are formed by revolving either a right angle or a rectangular in 360 degrees. So as you can see, cylinder has generators instead of edges or faces. So this is the top base which is circular and the bottom base which is circular. The line joining the center of top base and bottom base is your axis. So it has generators and no edges. So these are the types of solids or in which solids can be classified polyhedron and solids of revolution. Let us look further into what are the different types of solids further. This is a square pyramid and a hexagonal pyramid, a type of polyhedron in which they do not have top surface, a flat surface. They have a point called as apex whereas bottom might be any polygon. As here you can see it is a square. So this is a square pyramid which has an apex at the top. Instead of rectangular faces they have triangular faces whereas in prisms you have rectangular faces. Similar is the case with this hexagonal pyramid. The base is an hexagon and at the top you have the apex. So it has the triangular faces. So these are the types of polyhedron and in that pyramid. Let us move on to what are the different types of cutting planes. The first condition is plane perpendicular to VP and parallel to HP. Let us consider the vertical and horizontal plane that is HP and VP and a plane which is perpendicular to VP and parallel to HP. So this is the condition that we are considering. Now let us project the projection of this plane over VP and HP. So in VP projecting this plane we get an line view and the direction of observation is from the top. So this particular plane helps to find out or helps to give the sectional top view. Let us plot this projection on two dimensions. So this is your XY line. Now this being the front view it will be seen in VP. So this is the projection of this cutting plane which is perpendicular to VP and parallel to HP. Moving on to next. Plane perpendicular to HP and parallel to VP. Consider the principal planes. The plane which is perpendicular to HP and parallel to VP. So as you can see this. So this is your HP and VP naming. Now projection of this plane on HP as it is seen and we get a line view. So this is the required cutting plane which you can see in red color. This is the projection of this plane which is parallel to VP and perpendicular to HP. Plotting this over two dimensions XY line. Now this will be seen in top view that is at this area below XY line. So direction of observation is this. So you will get sectional front view when this kind of cutting plane is used. Moving on to next. Plane perpendicular to VP and inclined to HP. These are the principal planes. The required plane which is perpendicular to VP and inclined to HP. Projecting this in the front view that is on VP we get a inclined line. Further its projection on two dimensions XY line and front view. So this kind of plane can be used or gives sectional front view. Moving on further. Plane perpendicular to HP and inclined to VP reference planes HP and VP. So this is the plane which is perpendicular to HP and inclined to VP. Projection of this plane on HP we get a inclined line in the top view. Position of observation. This kind of plane is used to get the sectional front view or sectional side view. This is the XY line HP and VP in two dimensions and this is the required cutting plane which is inclined to VP and perpendicular to HP. Plane perpendicular to HP and VP. Now this condition the plane is perpendicular to both HP and VP. So taking projection of this plane on HP as well as VP. Projection on HP, projection on VP. Both the views will be a line view. These kind of cutting planes can be used to draw sectional side views. Its projection on two dimensions HP and VP. So this is the front view and this is the top view. So I hope you are clear with the idea of how cutting planes can be positioned or what are the different conditions that cutting plane can exist. These are the references. Thank you.