6 PKOBLEMS IN STRENGTH OF MATERIALS 



through the axis of the cylinder. How much must the bolt be 

 stretched by screwing up the nuts in order that the heads may be 

 held steam-tight against the flanges ? 



55. Determine the diameter of a steel piston-rod for a piston 20 

 inches in diameter and a steam pressure 90 pounds per square inch, 

 if the maximum unit-stress in the rod is to be 5000 pounds per 

 square inch. Find the lengthening and shortening of the rod per 

 linear foot under the pull and thrust. 



56. A steel piston-rod is 9 feet long and 8 inches in diameter; 

 the diameter of the cylinder is 88 inches, and the maximum effect- 

 ive pressure 40 pounds per square inch. Find the maximum unit- 

 stress in the rod and the total alteration in length during a 

 revolution. 



57. A piston-rod of structural steel is 4 inches in diameter and 6 

 feet long. If the piston diameter is 30 inches, what maximum steam 

 pressure may be used with a factor of safety of 10, and what is the 

 lengthening and shortening of the rod? 



58. A tie-rod 100 feet long and 2 square inches in sectional area 

 carries a load of 32,000 pounds, by which it is stretched | inch. 

 Find the unu>stress, unit-elongation, and the modulus of elasticity. 



59. A beam 12 feet long is suspended horizontally by vertical 

 wrought-iron rods at each end. The rod at left end is 1 inch square 

 and 12 feet long, while the rod at opposite end is J- inch square 

 and 3 feet long. What concentrated load should be applied to the 

 beam, and how far from the right end must it be placed, in order 

 that each rod shall be stretched to just one half its elastic limit? 

 Weight of beam and rods neglected. What is the elongation of 

 each rod? 



60. Calculate the elongation of the rod in Problem 16, due to its 

 own weight. 



61. A vertical wooden bar 100 feet long and 6 inches square car- 

 ries a load of 21,000 pounds at its lower end. Find the unit-stress 

 at the upper end and the elongation of the bar due to combined 

 weight of bar and load. 



62. Find the length of a vertical wooden bar 6x4 inches cross- 

 section, and having a load of 17,000 pounds at lower end, so that the 

 unit-stress at upper end, due to the combined weight, shall be one 



