In the course of the above research, they discovered that this spider silk has an ultimate strength #or tensile strength of 1850mPa (see 11.4 in University Physics). Tensile stress is a measure of the pressure in an object when it is stretched. Tensile strength is the maximum tensile stress that the object can endure before breaking. The equation for tensile stress is Tensile Stress=F/A where is the applied force F and A is the cross-sectional area of the object (in this case, the circle formed by a cross-section of a fibre). Ok, phew, so on to the question... If Spiderman has mass 63.2kg , what is the minimum diameter of fibre (of C. darwini spider silk) required to support his weight? I know that the area of a circle is Pi*r^2 but when I plug everything in I always get the wrong answer. I used force as mg, which didn't work. Could anyone please help?