66 



FALLING BODIES. 



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be represented by a horizontal line divided into equal 

 parts, each part representing a space equal to the velocity. 



The force of gravity may be 

 represented by a vertical line 

 divided into unequal parts, 

 representing the spaces 1, 3, 5, 7, 

 etc., over which gravity would 

 move it in successive seconds. 

 Constructing the parallelograms 

 of forces, we find that at the 

 16 end of the first second the ball 

 will be at A, at the end of the 

 next second at B, at the end of 

 the third at C, at the end of the 

 25 fourth at D, etc. The result- 

 ant of these two forces is a curve 



FIG. 30. 



called a parabola. It will be seen that, in a case like this, 

 the range GE may be found by multiplying the velocity 

 by the number of seconds it will take the body to fall 

 from F to G. The resistance of the air modifies the 

 nature of the curve somewhat. 



136. Time of a Projectile. From the second 

 law of motion, it follows that the ball shot horizontally 

 will reach the level ground in the same time as if it had 

 been dropped ; that the ball shot obliquely upward from a 

 horizontal plain will reach the ground in twice the time 

 required to fall from the highest point reached. These 

 statements may be easily verified by experiment. 



