पदार्थों के यांत्रिकी (mechanics of materials) में, बीम क्रॉस-सेक्शन के खंड मापांक (section modulus) को पारंपरिक रूप से किस अक्षर द्वारा दर्शाया जाता है?

When a bar of length l and uniform cross-section is rigidly fixed at the upper end and hangs freely, the total elongation produced in the bar due to its own weight is given by (where w = weight per unit volume and E = Modulus of Elasticity):

The hoop stress set up in a thin cylinder subjected to internal fluid pressure is: