41) What are the planes of projection ?

Vertical plane(VP) and Horizontal plane (HP) are generally used in orthographic projection. These planes of an object are obtained to describe it clearly with all dimensions. These are known as principle planes and the position of an object can be fixed by following four quadrants:
(1) First Quadrant: It is above HP and in front of VP.
(2) Second Quadrant: It is above HP and behind VP.
(3) Third Quadrant: It is below HP and behind VP.
(4) Fourth Quadrant: It is below HP and in front of VP.

42) Explain position of views in First Angle Projection ?

In first angle projection the top view is positioned below the front view with the left side view of the object to the right side of the front view.

43) What is the position of views in Third Angle Projection ?

The top view appears above the front view with right side of the object to the right of the front view in third angle projection.

44) What do you mean by Pictorial Drawing ?

It is a graphic language of engineers which represents a real thing by means of picture view.

45) What are the commonly used various methods of pictorial projection ?

(a) Isometric projection
(b) Oblique projection
(c) Perspective projection.

46) What is meant by Oblique projection ?

It is the one view projection where the projectors may be at any angle except 90 degree with the plane of projection, but 45 degree projectors are generally used because projectors at 45 degree with plane of projection all the edges of the cube are in their true lengths in the oblique projection.

47) What is an Isometric drawing ?

This is drawn by using three axis. One axis is drawn vertically and the other two are at an angle of 30 degree (right and left) to the horizontal.

48) Explain Perspective projection ?

A perspective drawing is one which more nearly present an object as seen in an actual photograph or as it appears to the eye of the observer.

49) What is a sectional view ?

The cross section of an object obtained by passing an imaginary cutting plane through the object is called sectional view.

50) Why is it necessary to show the sectional view of an object ?

Because it shows clearly the internal shape of an object or interior details of a part can easily shown