�ݺ�ߣ

-The shape of the solid is described by
drawing its two orthographic views usually
on the two principle planes i.e. H.P. & V.P.
PROJECTIONS OFSOLIDS
Definition of Solid:
A solid is a three dimensional object having
length, breadth and thickness. It is
completely bounded by a surface or surfaces
which may be curved or plane.
-For some complicated solids, in addition to
the above principle views, side view is also
required.
-A solid is an aggregate of points, lines and
planes and all problems on projections of
solids would resolve themselves into
projections of points, lines and planes.

Classification of Solids:
Solids may be divided into two main
groups;
(A) Polyhedra
(B) Solids of revolution
(A) Polyhedra :
A Polyhedra is defined as a solid
bounded by planes called faces which
meet in straight lines called edges.

There are seven regular Polyhedra
which may be defined as stated below;
(3) Tetrahedron
(4) Cube or Hexahedron:
(5) Octahedron:
(6) Dodecahedron:
(7) Icosahedron:
(1) Prism
(2) Pyramid

(1) Prism:
It is a polyhedra having two
equal and similar faces
called its ends or bases,
parallel to each other and
joined by other faces which
are rectangles.
-The imaginary
line joining the
Centres of the
bases or faces is
called Axis of
Prism.
Axis
Faces
Edge

According to the shape of its base, prism can be sub classified into
followingtypes:
(a)TriangularPrism:
(b)SquarePrism:

(c)PentagonalPrism:
(d)HexagonalPrism:

(2)Pyramid:
This is a polyhedra having plane
surface as a base and a number
of triangular faces meeting at a
point called the Vertex or Apex.
-The imaginary
line joining the
Apex with the
Centre of the
base is called
Axis of pyramid.
Axis
Edge
Base

According to the shape of its base, pyramid can be sub classified into
followingtypes:
(a)TriangularPyramid:
(b)SquarePyramid:

(c)PentagonalPyramid:
(d)HexagonalPyramid:

(B)SolidsofRevolutions:
When a solid is generated by revolutions
of a plane figure about a fixed line (Axis)
then such solids are named as solids of
revolution.
Solids of revolutions may be of following
types;
(1) Cylinder
(2) Cone
(3) Sphere
(4) Ellipsoid
(5) Paraboloid
(6) Hyperboloid

(1) Cylinder:
A right regular cylinder is a solid
generated by the revolution of a
rectangle about its vertical side
which remains fixed.
Rectangle
Axis
Base

(2)Cone:
A right circular cone is a solid
generated by the revolution of a right
angle triangle about its vertical side
which remains fixed.
Right angle
triangle
Axis
Base
Generators

ImportantTermsUsedinProjectionsofSolids:
(1)Edgeorgenerator:
For Pyramids & Prisms, edges are the
lines separating the triangular faces or
rectangular faces from each other.
For Cylinder, generators are the
straight lines joining different points
on the circumference of the bases with
each other

(2) Apex of solids:
For Cone and
Pyramids, Apex
is the point
where all the
generators or
the edges meet.
Apex
Apex
Edges
Generators
CONE
PYRAMID

Axis
Faces
Edge
PRISM
Rectangle
Axis
Base
Generators
CYLINDER

(3) Axis of Solid:
For Cone and Pyramids, Axis is an
imaginary line joining centre of
the base to the Apex.
For Cylinder and Prism, Axis is an
imaginary line joining centres of
ends or bases.

(4) Right Solid:
A solid is said to
be a Right Solid
if its axis is
perpendicular to
its base.
Axis
Base

(5)ObliqueSolid:
A solid is said
to be a Oblique
Solid if its axis
is inclined at
an angle other
than 90° to its
base.
Axis
Base

Important Terms Used in Projections
of Solids:
(6) Regular Solid:
A solid is said to be a Regular Solid if
all the edges of the base or the end
faces of a solid are equal in length and
form regular plane figures

of Solids:
(7) Frustum of Solid:
When a Pyramid or a
Cone is cut by a Plane
parallel to its base,
thus removing the top
portion, the remaining
lower portion is called
its frustum. FRUSTUM OF A
PYRAMID
CUTTING PLANE
PARALLEL TO
BASE

of Solids:
(8) Truncated Solid :
When a Pyramid or a
Cone is cut by a Plane
inclined to its base,
thus removing the top
portion, the remaining
lower portion is said to
be truncated.

Class A(1): Axis perpendicular to H. P. and hence
parallel to both V.P. & P.P.
X Y
a
b
d
c
c’,d’
a’,b’
o’
o
Axis

c’,3’
b’,2’
Class A(2): Axis perpendicular to V.P. and hence
parallel to both H.P. & P.P.
f’,6’
a
e’,5’
d’,4’
a’,1’
b,f c,e d
4
3,5
2,6
1
X Y
H

b”2”
1
a”1”
1’2’
Class A(3): Axis perpendicular to P.P. and hence
parallel to both H.P. & V.P.
X Y
L
c”3”
a’,b’
c’
a
b
c 3
2
3’

Class B(1): Axis parallel to V.P. and inclined to
H.P. by θ & also inclined to P.P.
Exercise 1 :
A right regular pentagonal prism,
side of base 30 mm and height of
axis as 75mm rests on HP on one
of its base corners such that its
long edge containing the corner is
inclined to the HP at 60°. Draw its
projections.

a’
5
c1’
X Y
31’
21’
4
11
51
41
21
31
a1
d1
c1
b1
e1
d1’ b1’
e1’
a1’
c’
d’
b’
e’
11’
51’
41’
a
b
e
d
3
2
1
60°
30
SCALE:-1:1
75
c

Exercise 2 :
A tetrahedron of 40 mm
long edges, rests on HP on
one of its edges such that
the face containing that
edge is inclined to HP at
30° and the same edge is
inclined at 45° to VP. Draw
the projections of the solid.

30
a
b
c
d
a’
d’
b’
c’
b1’
c1’
a1’
d1’
b
c1
a1
d1
a2’
d2’
b2’ c2’
X Y
40
45 c2
b2
a2
d2

30
a
b
c
d
a’
d’
b’
c’
b1’
c1’
a1’
d1’
b1
c1
a1
d1
a2’
d2’
b2’ c2’
X Y
40
45 c2
b2
a2
d2

A cone, diameter of base 60mm and
height 70mm, is resting on HP on
the point of periphery of the base.
Axis of the cone makes 60 with HP
and 30 with the VP. Draw the
projections of the cone, when the
apex is nearer to the VP.
Exercise 3 :

O’
70
60
a’
b’,h’ d’,f’
e’
c’,g’ e1’
a1’
O1’
60
O2
Locus of
O2
30
a e
f
g
h
b d
c
O2’
a2’
e2’
c2’
g2’
Y
X
O1
a1
c1
e1
g1
O
g2
a2
c2
e2
O

Exercise 4 :
A regular pentagonal prism of
25mm long edges and axis
70mm long rests on HP on one
of its corner of the base. The
slant edge passing through
corner makes 45 with HP and
the side opposite to the same
corner makes 30 with VP.
Draw its projections.

d1
e1
a1
b1
c1
b
a
c
d
e
1
2
3
4
5
d’
c’
b’
a’ e’
11
21
31
41
51
a1’
b1’
c1’ d1’
e1’
42’
12’
22’
32’ 52’
d2’
c2’
b2’ a2’
e2’
12
22
32 42
52
=45
= 30
1’
2’ 3’
5’
4’
e2
d2
c2
b2
a2
31’ 41’
51’
11’
21’
X Y

Exercise 5 :
A regular hexagonal prism of
30mm sides and axis 80mm
long is resting on HP on one
of its corners of the base. The
axis makes 30 with HP and
plan of the axis makes 45
with the VP. Draw its
projections.

a2
d2
b2
f2
c2
e2
12
22 42
62
32
52
d1’
b1’
a1’
c1’
e1’
f1’
21’
11’
31’41’
51’
61’
a1 d1
c1
b1
e1
f1
4’
2’ 3’
1’
5’
6’
d’
f’ e’
c’
b’
a’
X Y
5
1 4
2 3
6
e
a d
c
b
f
11
21 31
41
51
61
b2’
a2’
c2’ d2’
e2’
f2’
12’
32’
22’
42’
52’
62’
45

A square pyramid, side of base
50mm and height 64mm, is freely
suspended from one of the
corners of the base. Draw its
projections when vertical plane
containing axis makes an angle of
45 with the VP.
Exercise 6 :

A cube of 40 mm edges, is resting
on the H.P. on one of the edges of
the base with face containing that
edge making 30 with the H.P.
The edge on which the cube rests
on the H.P. is making 30 with the
V.P. Draw the projections.
Exercise :

�ݺ�ߣ

unit 3.pptx

Recommended

More Related Content

Similar to unit 3.pptx (20)

More from ArivazhaganRanganath1 (8)

Recently uploaded (20)

unit 3.pptx