4 PROBLEMS IN STRENGTH OF MATERIALS 



35. A cubical structural steel block J inch square rests on a 

 wrought-iron plate ^ inch thick and sustains a load of 10,000 

 pounds. Determine the factor of safety of the plate against being 



punched through by the block, and of 

 the block against being crushed. 



36. A cylinder 9J- inches inside diame- 

 ter contains steam whose maximum pres- 

 sure is 200 pounds per square inch. The 

 steel piston-rod which projects through 

 the piston has a nut on one side of the 

 piston, and a shoulder on the other side, 



FIG. 1 



which carries the compressive load on the 



rod. Find the diameter of the rod through the piston, and that of 

 the shoulder for a factor of safety of 8 against tension and compression. 



II. ELASTIC DEFORMATION 



37. A bar 1 inch in diameter and 8 feet long elongates 0.05 inch 

 under a tension of 12,000 pounds. How much will a bar of the same 

 material and diameter, 12 feet long, elongate with a pull of 30,000 

 pounds ? 



38. Compute the modulus of elasticity for the steel specimen of 

 Problem 9. 



39. A copper wire 0.04 inch in diameter and 10 feet long stretches 

 0.289 inch under a pull of 50 pounds. Find its modulus of elasticity. 



40. A wooden specimen 1 inch in diameter and 9 inches long 

 elongates 0.004 inch when the tension is increased from 500 to 1000 

 pounds, and 0.10 inch when the tension is increased from 1500 to 

 5000 pounds. Find the modulus of elasticity. 



41. Determine the elongation of a l^-inch round wrought-iron rod 

 10 feet long, under a tensile load of 24,600 pounds. 



42. A wrought-iron rod 2 inches square and 10 feet long lengthened 

 0.03 inch by suspending a load from its lower end. Determine the 

 load. 



43. A wrought-iron bar 10 feet long sustains a load ^ as great as 

 would be required to pull the bar apart. Determine the elongation 

 of the bar, also the load if the bar is 1^ inches square. 



