FORCE 21 



22. Exercises. 



1. Name five phenomena, besides those of 18, that are "changes 

 in the position of bodies." 



2. Suppose that the moon and the earth were of exactly the same 

 mass, and that a ball weighing a ton were placed half-way between 

 them. What would its weight be? 



Why? 



3. If you dropped wooden, iron, and 

 lead balls from an upper window, which 

 would reach the ground first? 



4. Suppose the wind were blowing 



hard down the street, and you dropped 



a tennis ball from an upper window. 



Where would it strike the ground? 

 Why? 



5. Draw a diagram to show the kind T , FIG - 17 * 



.. ,. in, . The Marbles Reach the Floor at the 



of a path a ball takes if you throw it Same instant, 



horizontally. If you throw it upward 



at an angle of 45 degrees (half a right angle). In which case would 

 the ball have the greater range? 



6. Who was Sir Isaac Newton? When did he live, and where? 

 What did he add to our knowledge? 



Answer the same questions regarding Galileo. 



23. Force. Let us imagine we are at a baseball game. 

 The pitcher throws a "fair" ball, the batter strikes at it 

 but makes a "foul" hit, and the catcher catches the ball. 

 Three persons were concerned in the flight of that ball: 

 the pitcher, who set it in motion; the batter, who changed 

 the direction of its motion; and the catcher, who stopped 

 its motion. We say that all three exerted force upon the 

 ball. 



Besides the players, two other bodies exerted force upon 

 the pitched ball: (1) the air, which resisted being pushed 



