Lesion. VIII.] 



MKCHANICS. 



87 



with diameters as the even numb. : 



\ ., tor the upper block. The cord 



grooves, as 



and is thrown oil" 



-.m., manner as if every groove was 



a separate revolving wheel. 



1IONS ON LESSON V!I. 

 1. What is the funicular machine ? 



A hy have pulleys round shea. 



3. What is a pulK-y ? 



4. Describe the difference between fixed 

 and movable pull 



.".. How can you maintain equilibrium 

 in a pulley ? 



6. Does the movable pulley possess 

 any advantage over the fixed pulley I 



7. How do pulleys act? 



8. How can pulleys be increased in 

 power ? 



y. What is White's pulley?" 



I.KSSON VIII 



THF. inclined plane is the most simple of all machines, and perhaps the most 



familiar. Roads and railroads often present instances of the application of this 



principle to practical and useful purposes. In applying this machine, it is generally 



^ed to be fixed, and the weight or load to be the movable body ; but, sometimes, 



it is necessary to move the inclined plane whiie the body or load is partially fixed. 



QUESTIONS. 



100. T. What is generally understood 

 by the term, an inclined plane ? 



unifies a plane surface, per- 



. and unyielding, inclined in 



such a manner, that it forms some angle 



iutal plane, but not a right 



angle. 



T. What do you mean by a plane 

 i. and forming an 

 angle with a horizontal plane. 



will explain 

 I .-my. A I'. 

 tents the 

 plane, or a surfai 



A I) 11 is n right 



/,, r,. 



line A B; AC 

 plane, or nl 



an acute .< .with 



re, the 



i the object of uing 

 the inclined | 



P. To raise weights to great n. 



the ap; "eight. 



T. How is the advantage gained 



by this machine estimated? 



P. Hy subtracting the perpendicular 

 :rom the length of the plane, and 

 ,.uct, or excess of length, show* the 



advantage gained. Suppose the height, 



.nclined pi.. ;i!ed in 



<>ne loot, and the hit-lined 



he four tret ; thm a 



W) t.| four pounds placed on the 



y a weight 



pound (!') hanging over a pulley at the 

 end ot :it tli.it Ole- 



I'oursh of the power p-ipmed to raise a 



through the space B C. 

 it up the iiiflnii .I plane t 

 III all eases win 



ist be made 



KIK / n,.. . 



<1 plane afford us murh 

 /' I ;, . h as raimn. 



loads to considerable heights ; but I 



