286 



Dynamics* 



This case takes place when the machine is employed in raising 

 a weight, drawing water, &c. 



When i = O,/ = and m = p, then m + ior5=_p=l, and 



When D = <5, as in the common pulley, then <S = 1, and 



r = - = -v/2 1 = 0.4142. 



In order to save the trouble of calculation, we have added the 

 following table, computed from the formula 



6* 



Table containing the best Proportions between the Power and Resist- 

 ance, the Inertia of the impelling Power being the same with its 

 Pressure, and the Friction and Inertia of the Machine being 

 omitted. 



In order to understand the method of using this table, let us 

 suppose that it is required to find the value of the resistance, or 

 the quantity of water which must be put into a bucket to be 

 raised by a wheel and axle, in which the radius of the wheel is 

 6 feet, and that of the axle 2 feet, and with a power = 8. Since 

 in the table, D = l,we have 



