42 PROBLEMS IN STRENGTH OF MATERIALS 



4800 Ib. 



384. 



x* 



540/6. 



385. 



12'- 



J000 Z6 

 386. V 



,2000 Z6. 



C 



387. 



100 Ib. per ft 



00 Ib. 



12'- 



389. A cast-iron hollow cylindrical beam 30 feet long and fixed at 

 both ends has an external diameter of 10 inches and an internal 

 diameter of 8 inches. What load can it support at the middle with a 

 factor of safety of 6, and what will then be the maximum deflection ? 

 Neglect weight of beam. 



390. What steel I-beam with fixed ends is required for a span of 

 20 feet to support a total uniform load of 20,000 pounds, with a 

 maximum unit-stress of 15,000 pounds per square inch? Find also 

 the maximum deflection. 



391. An 8-inch steel I-beam, 18 pounds per foot, with fixed ends 

 and 8 feet span, is loaded at the middle so that the maximum unit- 

 stress is 16,000 pounds per square inch. Find the maximum deflection. 



