COMBINED STRESSES 53 



508. Determine the factor of safety fo^A simple wooden beam 8 feet 

 long, 10 inches wide, and 9 inches deep, tinder an axial tension of 

 40,000 pounds, and bearing a total uniform load of 4200 pounds. 



509. A wooden cantilever beam 3 feet long, 3 inches wide, and 4 

 inches deep has a load of 300 pounds at the free end, and is under 

 an axial tension of 4500 pounds. Compute the maximum tensile and 

 compressive unit-stresses, neglecting the weight of the beam. 



510. Find the size of a square, wooden simple beam of 12 feet span, 

 which bears a total uniform load of 50 pounds per linear foot, and at 

 the same time is under an axial tension of 2000 pounds, the maxi- 

 mum allowable unit-stress being 1000 pounds per square inch. 



511. A bolt 1 inch in diameter is subjected to a longitudinal tension 

 of 5000 pounds, and at the same time to a cross-shear of 3000 pounds. 

 Determine the maximum combined tensile and shearing unit-stresses, 

 and the angles they make with the axis of the bolt. 



512. Find the maximum unit-stresses in a circular steel shaft 

 6 inches in diameter, resting on supports 10 feet apart, and trans- 

 mitting 50 H.P. at 225 E.P.M., due to the combined bending and 

 torsional moments. 



513. Determine the diameter of a solid wrought-iron shaft 12 feet 

 between bearings and transmitting 50 H.P. at 130 R.P.M., if pulleys 

 are placed so as to produce a maximum bending moment of 600 

 pound-feet at the middle, and the maximum combined unit-stress is 

 10,000 pounds per square inch. 



514. A bar of iron is under a direct tensile stress of 5000 pounds 

 per square inch and a shearing stress of 3500 pounds per square 

 inch. Find the maximum tensile and shearing unit-stresses. 



515. A wrought-iron shaft is subjected simultaneously to a bending 

 moment of 8000 pound-inches and a twisting moment of 15,000 

 pound-inches. Determine the least diameter of the shaft if the maxi- 

 mum tensile strength is not to exceed 10,000 pounds per square inch, 

 and the shearing stress 8000 pounds per square inch. 



516. Find the diameter of a wrought-iron shaft to transmit 90 H.P. 

 at 130 E.P.M., with a factor of safety of 5, if there is also a bending 

 moment equal to the twisting moment. 



517. A wrought-iron shaft 3 inches in diameter and making 140 

 RP.M. is supported in bearings 16 feet apart. If a load of 210 pounds 



