30 PROBLEMS IN STRENGTH OF MATERIALS 



253. Find the total uniform load that a wooden floor beam 2x10 

 inches in rectangular section and 16 feet long will carry with a factor 

 of safety of 8. 



254. Solve Problem 253 with the 10-inch side horizontal. 



255. A simple wooden beam 3 inches wide, 4 inches deep, and 16 

 feet long bears a concentrated load of 140 pounds at the middle. 

 Determine the factor of safety if the weight of the beam is neglected. 



256. Find the factor of safety for the beam of Problem 255, taking 

 into account the weight of the beam. 



257. A piece of scantling 2 inches square and 8 feet long is sup- 

 ported at its ends, and sustains a load of 150 pounds at its middle. 

 Is it safe ? Neglect weight of beam. 



258. A wooden beam 4 inches square, resting on end supports, is 

 to carry a uniform load of 40 pounds per linear foot, including its 

 own weight. Find the maximum safe distance between supports. 



259. A wooden beam 4 inches broad, 6 inches deep, and 10 feet / 

 long is supported at its ends. Calculate the load it can carry at its ^ 

 middle point with a factor of safety of 8, if weight of beam is neglected. 



260. Solve Problem 259, considering weight of beam. 



261. The piston of a steam engine is 14 inches in diameter, and the 

 steam pressure 80 pounds per square inch. Assuming that the total 

 pressure on the piston comes on the crank pin at the dead points, and 

 that the crank pin is a cantilever uniformly loaded, what should be 

 its diameter if 4 inches long and made of wrought-iron ? Use a factor 

 of safety of 10. 



262. A steel engine shaft resting on bearings 5 feet apart carries a 

 3-ton fly-wheel midway between the bearings. Find the diameter of 

 the shaft to carry this load with a factor of safety of 10. 



263. A wooden cantilever 8 feet in length and 4 inches broad bears 

 a total uniform load of 80 pounds per linear foot, and concentrated 

 loads of 600 and 200 pounds at 3 and 8 feet respectively from the 

 support. Determine the depth of the beam, using a factor of safety 

 for steady stress. 



264. Find the factor of safety for a structural steel engine shaft 

 12 inches in diameter, resting in bearings 54 inches apart and carry- 

 ing a fly-wheel of 40 tons midway between the bearings. Neglect 

 weight of shaft. 



