THE MECHANICAL POWERS. 291 



EXAMPLE. What is the force required to raise 600 Ibs. 

 by means of a lower block containing six sheaves : rope 

 fastened to the upper block? 



SOLUTION. 2 x 6=12 ; then, 600-7-12=50 Ibs. Ans. 



EXAMPLE 2d. What force when the rope is fastened to 

 the lower block ? 



SOLUTION. 6x2 + 1=13; then 600 -r 13=46.16 Ibs. Ans. 



When more than one rope is used. 



In a Spanish Burton, where there are two ropes, two 

 movable pulleys, and one fixed and one stationary pulley, 

 with the ends of one rope fastened to the support and 

 upper movable pulley, and the. ends of oe other fastened 

 to the lower block and the power, the weight is to the 

 power as 5 to 1. 



In one where the ends of one rope are fastened to the 

 support and the power, and the ends of the other to the 

 lower and upper blocks, the weight is to the power as 4 to 1. 



