24 BULLETIN 556, U. S. DEPABTMEXT OF AGKICULTTJEE. 



WORK. 



fSee p. 15.) 



Work is the product of force and distance, or force acting through 

 distance. 



Work is essential in stopping bodies in motion, or in causing motion 

 or change of motion of bodies. 



Work is measured in inch-pounds, foot-pounds, etc. 



An inch-pound is the work required to raise one pound 1 inch or to 

 more a body 1 inch against a resistance of 1 pound. 



FORMULA USED IN COMPUTING. 



LEGEND. 



A = Area of cross section; square inches. 



B=Area under plate in compression-perpendicular-to-grain tests, 



square inches. 

 CS = Crushing strength, pounds per square inch. 



E = Modulus of elasticity, pounds per square inch. 

 EL = Fiber stress at elastic limit, pounds per square inch. . 

 J = Greatest calculated longitudinal shear, pounds per square inch. 

 K = Constant = 27.7 when weight is in pounds; 0.061 when weight 

 is in grams. 

 MR ■ = Modulus of rupture, pounds per square inch. 

 P= Maximum load, pounds. 

 P' =Load at elastic limit, pounds. 

 S = Dry specific gravity. 



A = Total deflection or compression at elastic limit, inches, 

 b = Width, inches 



d = Distance between centers of collars, inches. 

 li = Height, inches. 

 l = Span, inches (in compression parallel to grain 1 = length). 



BENDING. 



Load applied at center: 

 T 0.75XP 



bxh 



1.5XPX1 



MR = 



EL = 



E= 



bxh 2 

 1.5XP'X1 



bxh 3 

 P'xl 3 



4 X b X h 3 X A 



