1. The problem statement, all variables and given/known data A cylindrical rod has a spherical bubble in it. as illustrated in figure 4.2 (in the attachments) The rod has a cross sectional area of 3.2 x 10^-6 m^2 and is stretched by forces of magnitude 1.9 x 10^3 N. The maximum Stress that the cylinder can take is 9.5 x 10^8 Pascals. 2. Relevant equations Stress = Force/ Cross sectional area 3. The attempt at a solution Basically what I did was say: Maximum stress = Force applied/Area 9.5 x 10^8 = 1.9 x 10^3 / Minimum area Minimum area = 2 x 10^-6 m^2 So the maximum Cross sectional area of a rod is 2 x 10^-6 m^2 The right answer was on the other hand to do all this + subtract new area from old area so it becomes (3.2 - 2) x 10^-6 = 1.2 x 10^-6 This is the part I don't understand. Shouldn't the maximum cross section of the ball be the area of the new cylinder so that if it is more then the cylinder breaks???