The plane which is parallel to base will definitely cut cone at all generators. Here additional information also given that plane is parallel to base so cross-section will be circle.

In a Double-threaded screw, Pitch of helix = lead = Twice pitch of screw, similarly in a triple-threaded screw, pitch of helix = lead = Thrice pitch of screw and so on.

The fixed straight line is called as directrix and fixed point is called as a focus. Eccentricity is defined as ratio of distance from focus to distance from directrix and it is denoted by e. Hence from definition e = 14 ÷ 5 = 2.8.

Outer diameter is equal to sum of inner diameter and 2 times diameter of a wire. Here cross section of wire is square so diameter can be considered as 15 mm. outer diameter = 60 +2 x 15 = 90 mm.

Eccentricity is defined as ratio of distance from focus to distance from directrix and it is denoted by e. Therefore, by definition, e = 3 ÷ 5 = 0.6. Hence conic section is called an ellipse.

Eccentricity is defined as ratio of distance from focus to distance from directrix. Hence from formula of eccentricity, e = 10 ÷ 30 = 0.3333. Since value of eccentricity is less than one conic is an ellipse.

Spring index is ratio of mean diameter of coil to diameter of wire. 12.5 = mean diameter of coil / 5mm, mean diameter of coil = 12.5 x 5 mm = 62.5 mm. We need to use same units while substituting in formulae.

Conic sections are formed when a plane cuts through cone at an angle with respect to axis of cone. If angle is right angle n conics is a circle, if angle is oblique n resulting conics are parabola and ellipse.

Whatever end diameters of a conical spring number of revolutions depends on pitch and height of spring. Number of revolutions = length of spring/pitch of helix = 80 mm/5 mm = 16.

2 revolutions = 40 mm so 1 revolution = 40 mm/ 2 = 20 mm. In any type of screw, advancement of screw for one revolution is equal to pitch of helix. So here also pitch of helix is 20 mm.