HOW TO WEIGH 5 



b. The Capacity of a Measuring Cup. Examine a measur- 

 ing cup with vertical sides. We can calculate its capacity, or 

 how much it holds, in cubic centimeters, as follows : 



Measure carefully the inside, vertical height, from the bot- 

 tom of the cup to the lower edge of a ruler, of block, placed 

 across the top. Have it accurate to 0.1 of a cm. Measure also 

 the greatest inside distance across the top (the diameter) . The 

 capacity of the cup is equal to the height multiplied by -f^XiX 

 the square of the diameter. Suppose that a cup has a diameter 

 of 3 cm., and a height of 4 cm. The capacity of the cup 

 would be 4X?XiX9, or 28.28+ cu. cm. 



How many cubic centimeters does your cup hold? Fill the 

 cup with water, then pour the water carefully into a graduated 

 cylinder. How does your calculated result compare with that 

 shown by the cylinder? 



Use the table of equivalents in the Appendix of the text to 

 find the capacity of your cup in cubic inches. A gallon is 

 equivalent to 231 cu. in. How many of your cupfuls are there 

 in a gallon? In a quart? In a pint? Does your measuring 

 cup seem to be fairly accurate, as judged by the number of 

 cupfuls in a pint? 



EXERCISE 4 

 HOW TO WEIGH 



Apparatus and Materials. Balances, weights, shot, graduated 

 cylinder, measuring cup or beaker, water. 



a. Balances. We weigh objects by means of balances or 

 scales (see Figs. 9, 10, and 11 of the text). Fig. 5 (this manual) 

 represents some home-made scales; they can be hung from an 

 overhead support, such as the edge of a shelf or the ring of a 

 ring stand. The beam is of galvanized iron or sheet copper; 

 the pans may be the covers of small baking-powder boxes; the 



