/* -------------------------------------------------------------------------   
// Figure 6.12  Repeating a calculation.
// Figure 6.13  The work() and drop() functions.
// -------------------------------------------------------------------------   
//     Determine the time it takes for a grapefruit to hit the ground when   
//     it is dropped from a helicopter hovering at height h, with no initial 
//     velocity. Also determine the velocity of the fruit at impact. Use a 
//     work function to perform the computations and output results. 
*/

#include "tools.h"       /* #include commands and user-defined utilities */ 

void work( void );  
double drop( double height );  

void main( void )                                                                                                              
{  
    int do_it_again;                /* repeat-or-stop switch */ 
 
    banner();                                       
    puts( "\n Calculate the time it would take for a grapefruit\n" 
          " to fall from a helicopter at a given height.\n" ); 

    do { work();
         printf( " \n\n Enter '1' to continue or '0' to quit: " ); 
         scanf( "%i", &do_it_again );           
    } while (do_it_again != 0);

    bye();            
} 

/* ------------------------------------------------------------------------   
// Perform one gravity calculation and print the results.   
*/  
void  work( void )          
{  
    double h;                /* height of fall (m) */             
    double t;                /* time of fall (s) */                
    double v;                /* terminal velocity (m/s) */  
 
    printf (" Enter height of helicopter (meters):  " );           
    scanf( "%lg", &h );                        

    t = drop( h );          /* calculate duration of fall.  */      
    v = GRAVITY * t;        /* velocity of grapefruit at impact  */  
    printf( "    Time of fall = %g seconds\n", t );                   
    printf( "    Velocity of the object = %g m/s\n", v ); 
} 

/* ------------------------------------------------------------------------   
// Calculate time of fall from a given height.   
*/ 
double 
drop (double height)      
{   
    if (height < 0) return 0;             
    else return sqrt( 2 * height / GRAVITY ); 
}  
/* ----------------------------------------------------------------- */