QUESTIONS AND PROBLEMS. CHAPTER I. 21 



35. A steel bar is 8 ft. long and two square inches in cross 

 section; its elastic limit is 30000 Ibs. per sq. in. and E = 29000000: 

 what must be the cross section of a cast iron bar of the same 

 length so that it will have the same elastic resilience, the elastic 

 limit being 10000 Ibs. per sq. in. and E= 12000000. 



Ans. 7.43 sq. in. 



36. In problem 12, what will be the ratio of the unit stress 

 in the steel to that in the concrete, for a unit deformation d 

 if E c and E at are, respectively, the moduli of elasticity of con- 

 crete and steel? 



