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UNIT-IISyllabus(a) Projection: Introduction, principle of projection, method of projection, planes of projection, four quadrants, first and third angle projection, reference line symbols for methods of projections, orthographic projection.

.Q. Explain orthographic projection.Q. What is orthographic projection? (S10)A. ‘ORTHO’ means right angle and ‘ORTHO-GRAPHIC’ means ‘right-angled drawing’ . When the projectors are perpendicular to the plane on which the projection is obtained, it is known as orthographic projection.

.Q. Why the projections of an object are not drawn in second and fourth quadrant. (W09)A. According to standard practice, horizontal plane is rotated away from the object. Due to the rotation second and fourth quadrants close. They are drawn on the same side of xy line . Sometimes front and top views may overlap. This creates confusion. That is why the projections of an object are not drawn in second and fourth quadrant.

.Q. Define auxiliary planes and classify it. (W09)Q. What are the different types of auxiliary planes? (S10)Any plane other than H.P. and V.P. is called auxiliary plane. Auxiliary planes can be classified asAuxiliary Vertical PlanesAuxiliary Inclined Planes

.Q. Describe first angle projection method. (W07)A. When the object is situated in first quadrant, it is in front of V.P. and above H.P., the projections obtained on these planes are called first angle projection. In first angle projectionThe object lies in between the observer and the plane of perpendicular.The front view is drawn above the XY line and the top view below XY line.Front view shows the length and height of an object. Top view shows length and breadth of it.

.Q. How do you denote first angle projection method and third angle projection method using symbols. (W06)

.2.1 A point ‘A’ is 15 mm above the HP and 20 mm in front of the VP. Another point ‘B’ is 25 mm behind the VP and 40 mm above the HP. Draw the projections of ‘A’ and ‘B’ keeping the distance between the projectors equal to 90 mm. Draw the straight lines joining (a) their views from above and (b) their views from the front. (W06)

.2.2 An electric switch (A) and a bulb (B) fixed on a vertical wall are 5 metres apart. The distance between them measured parallel to the floor is 4 metres. If the switch is 1.5 metres above the floor, find the height of the bulb and the inclination of the line joining the two with the floor. (W06)

.2.3 A line AB inclined at 30° to the HP has its ends A and B, 25 and 60 mm in front of the VP respectively. The length of the view from above is 65 mm and its V.T. is 15 mm above the HP. Draw the projections of the line and locate its H.T. (W06)

.2.4 Draw the projections of the following points on the same base line keeping the projections 25 mm apart. Point A in the HP and 25 mm behind the VP.Point B 15 mm above HP and 50 mm behind the VP. Point C, 40 mm above the HP and 25 mm in front of VP.Point D, in the VP and 40 mm above the HP. (W07)

.2.5 Draw the projections of a line AB when its end A is 20 mm above the HP and 10 mm in front of VP. Its end B is 55 mm above the HP and 60 mm in front of the VP and the distance between the projections A and B measured parallel to the xy line is 45 mm. Find the true length, Ө and ф of the line and locate its traces. (W07)

.2.6 A line AB, 65 mm long is inclined to HP at an angle of 45°. Its end point A is 15 mm above the HP and 25 mm in front of VP. Line AB is contained by a vertical plane making an angle of 45° to the VP. Draw the projections of the line. Find the inclination of the line with VP and locate its traces. (W07)

.(b) A line AB 90 mm long is inclined at 30˚ to the HP. Its end A is 12 mm above the HP and 20 mm in front of VP. Its front view measures 65 mm. Draw the top view of AB, and determine its inclinations with the VP and also HT and VT.

.(c) Three vertical poles AB, CD and EF are respectively 5, 8 and 12 meter long. Their ends are on the ground and lie at the corners of an equilateral triangle at 10 meters long side. Determine graphically the distance between the top ends of poles viz AC, CE and EA.

.Two lines AB and AC make an angle of 120˚ between them in the front view and top view. AB is parallel to both the HP and VP. Determine the real angle between AB and AC.

.(b) A point 30 mm above x y line is the plan-view of two points P and Q. The elevation of P is 45 mm above the HP while that of Q is 35 mm below HP. Draw the projections of the points and states their position with reference to the principal planes and the quadrant in which they lie.

.(c) In complete projections of a line PQ, inclined at 30˚ to the HP are given in the figure. Complete the projections and determine its true length and its inclination with the VP.

.Two oranges on a tree are respectively 1.8 and 3 m above the ground and 1.2 m and 2.1 m from 0.3 m thick wall, but on the opposite sides of it. The distance between the oranges, measured along the ground and parallel to the wall is 2.7 m. Determine the real distance between the oranges.

.(b) Point A, 7 mm above the HP and 15 mm in front of VP. Point B, 40 mm above the HP and 50 mm in front of VP. Projectors of point A and B are 50 mm apart. Draw the projections of line AB and find its HT, VT. Find the length of line AB.

.(c) A line AB 70 mm long has its end A at 10 mm above HP and 15 mm in front of VP. Its front view and top view measure 50 mm and 60 mm respectively. Draw the projections of the line and determine the inclinations with HP and VP.

.(d) A room is 4.8 m × 4.2 m × 3.6 m high. Determine graphically the distance between a top corner and bottom corner diagonally opposite to it.

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