EXERCISES 37 



A floating body is entirely supported. An immersed body is sup- 

 ported with a force equal to the weight of the liquid (or gas) displaced 

 by the body. 



The center of mass of a body is the point around which the matter 

 of the body is arranged. A body is in a stable position when its center 

 of mass is directly over some part of the base on which the body rests. 

 It is most stable when its center of mass is in the lowest possible posi- 

 tion. 



37. Exercises. 



1 . What is the chief force to be overcome when we drive a nail into 

 wood? 



2. Why does a drop of mercury on a table remain almost spherical, 

 while a drop of water does not? 



3. Why is it so hard to drv the hands on a new, unlaundered towel? 

 Why is writing paper "filled" or "sized"? 



4. Name the following substances in the order of their densities, 

 beginning with the lightest (see Appendix, Table III): iron, cork, 

 kerosene, lead, paraffin, aluminum, marble, zinc, gold, silver, copper, 

 water, alcohol, and milk. 



5. If one cubic foot of water weighs 62.5 Ibs., how much does a cubic 

 foot of iron weigh? 



6. How does the addition of a life preserver to a person's body alter 

 the weight of matter that must be supported by the water? How does 

 it alter the density? Why? 



7. Why does a steel ship float? 



8. We can find the volume of a body, such as a stone, if we weigh 

 the body first in air and then in water. Explain how. 



9. An iceberg may turn over after the part under water has melted 

 for a time. Why? 



10. How do you lean your body when you carry a pail of water? 

 When you run forward? When you climb a hill? Why? 



