WORK AND MACHINES 163 



products are the moments of P and of W. Infer when a 

 lever will be in a balanced condition, or state of equilibrium. 

 Make a drawing that shows the lever in some one of these 

 positions, and correctly locate on it the positions and values 

 of P and W. Label the drawing IST CLASS LEVER. 



2. Having the lever supported as before, put both P and 

 W on the same side of F, and with W between P and F. It 

 will now be necessary to pull upward with the spring balance 

 in order to maintain equilibrium. Calculate the moments 

 of W and of P in different positions, and state what is 

 true of their relative values in every instance. What 

 is true in every case (a) of the relative lengths of power 

 and weight arms (distances) ; (6) of the relative values 

 of Pand W? 



Make a drawing to represent the lever in some one of 

 these positions, and label it 2o CLASS LEVER. 



3. Arrange the lever now so that the pull of the balance 

 (P) is upward, and between W and F. State what is found 

 true under these conditions (a) of the moments of P and W ; 

 (b) of the relative values of P and W. Make a drawing to 

 represent a SD CLASS LEVER, putting upon it the values 

 found in some one of the cases for P and W, and for Pd and 

 Wd. 



PULLEYS 



(a) With the Cord Attached to the Fixed Pulley 



It is desirable to have a pair of "triple-tandem" pulleys as rep- 

 resented in the cut, and a spring balance graduated both in grams and 

 in ounces. A length of stout, smooth cord with loops at its ends is 

 easily provided. 



