172 



Journal of Agricultural Research 



Vol. xn. No. 4 



Table X. — Values of the direction cosines for normals, tangents to the path, and per- 

 pendiculars io the planes 



«=7-55 5^3-6 2= 18.4 



For the purpose of computing the forces a block of soil 2 inches wide, 

 I inch long, and )4 inch thick is taken. The mass of this soil is 



M= 



(2. 1. 5)62. 5p 0.0362P 



(81) 



1728.32.2. 12 32.2.12 

 p= density. 



By the proper substitutions from Tables IX and X into equations (60), 

 (61), and (62) the forces necessary to produce the accelerations are com- 

 puted and listed in Table XI. 



Table XI. — Forces necessary io produce acceleration in soil particles 



x= 7-55 

 Fn= .00S03P 



x=ii.S 

 Fii= .00281P 



x=ig.s 

 Fn= .00234P 



y= 3-6 

 Ft= .001 i6p 



y= 8.25 



Ft= .000248P 



y=ii 

 Ft= .00428P 



2=18.4 

 Fe= .002 52P 

 2=27.9 



^E= •OO592P 

 2=36 



Fb= .00778P 



A soil particle in passing over the surface of the plow bottom will be 

 acted upon by the following : 



(a) A force from the surface of the bottom acting in the direction of 

 the normal. 



(b) Gravity. 



(c) Pressure from the weight of the soil above the particle. 



(d) Friction between the particle and the surface. 



