1. The problem statement, all variables and given/known data For reasons based on cost,weight,availability , etc., the choice is made to construct the rod from aluminum of σall = 100 MPA. What is an appropriate choice for the rod diameter ? Givens: (P=50 KN) 2. Relevant equations 3. The attempt at a solution σall=P/A , then he get the Area and from area he then gets the Diameter=25.2mm Then he said an aluminum rod 26m or more in diameter is adequate My question is : why an aluminum rod of 26m or more in diameter is adequate ?!!