what happens if the ppf is a straight line
Production–possibility frontier In the context of a PPF, opportunity cost is directly related to the shape of the curve (see below). If the shape of the PPF curve is a straight-line, the opportunity cost is constant as production of different goods is changing. But, opportunity cost usually will vary depending on the start and end points. In the diagram on the right, producing 10 more packets of butter, at a low level of butter production, costs the loss of 5 guns (shown as a movement from A to B). At point C, the economy is already close to its maximum potential butter output. To produce 10 more packets of butter, 50 guns must be sacrificed (as with a movement from C to D). The ratio of gains to losses is determined by the marginal rate of transformation.
Line (geometry) When geometry was first formalised by Euclid in the Elements, he defined a general line (straight or curved) to be "breadthless length" with a straight line being a line "which lies evenly with the points on itself".[5] These definitions serve little purpose since they use terms which are not, themselves, defined. In fact, Euclid did not use these definitions in this work and probably included them just to make it clear to the reader what was being discussed. In modern geometry, a line is simply taken as an undefined object with properties given by axioms,[6] but is sometimes defined as a set of points obeying a linear relationship when some other fundamental concept is left undefined.