Page 142 - classs 6 a_Neat

A cylinder has a curved lateral surface and two circular faces at its ends. PYRAMID
A cylinder has no corner or vertex.
A cylinder has two plane faces, namely, the top and the base, (i) PYRAMID A pyramid is a solid whose base is a plane rectilinear figure and whose side faces are
and one curved face. It has 2 circular edges. triangles having a common vertex, called the vertex of the pyramid.
The distance between its end faces is called its length.
The length of perpendicular drawn from the vertex of a pyramid to its base is
called the heightof the pyramid.

The side faces of a pyramid are called its lateralfaces.

(ii) TRIANGULAR PYRAMID A solid whose base ts a triangle and whose side
faces are triangles having a common vertex is called a triangular pyramid.

SPHERE The adjacent figure shows a triangular pyramid OABC with O as vertex
and MBC as its base.
SPHERE An object which is in the shape of a ball is said
to have the shape of a sphere. A triangular pyramid has 3 triangular lateral faces,
one triangular base and 6 edges.
A sphere has a curved surface.
A sphere has no vertex and no edge. A triangular pyramid is also called a tetrahedron.

CONE 1. An object that occupies space ts called a solid.
2. Shapes of solids are known as three-dimensional shapes.
CONE Objects such as an tee-cream cone, a conical tent, a conical vessel, a clown’s cap, etc., 3. A matchbox, a chalk box, a brick are all examples of a cuboid.
are in the shape of a cone. 4. f’ cuboid has length, breadth and height.
5. A cuboid has 6 rectangular faces, 12 edges and 8 vertices.
Some examples of cones are given below.
1. In a polygon of “n” sides, the sum of all interior angles is (n -2) × 180°. What is the minimum
value of “n”?
2. By how many degrees does the minute hand revolve in 25 minutes?
3. What is a tetrahedron? When is it called a regular tetrahedron?
1. Identify the following as a point, a line or a plane:

a. location of cities in a map b. a stretched wire between two poles
c. floor of a room d. a sheet of a note book
A cone has a plane circular end as the base and a curved surface tapering into a point, e. the edge of a dice
called its vertex.
2. In the above figure, identify and write the following
Thus, a cone has one plane face (i.e. base) and one curved face.

It has one circular edge and one vertex.

TRIANGULAR PRISM

TRIANGULAR PRISM A solid whose lateralfaces are rectangular and the bases are congruent
triangles, ts called a triangular prism.

The adjoining figure shows a triangular prism, denoted by (ABC, PQR). a. the points marked b. all the line segments
A triangular prism has 6 vertices, 3 rectangular lateralfaces, 2 triangular bases and 9 edges. c. the planes formed