/* ---------------------------------------------------------------------  
// Figure 3.10:  Asking more than one question.                                        
// --------------------------------------------------------------------- 
*/
/* This program will determine the velocity and distance travelled by a  */
/* grapefruit with no initial velocity, t seconds after being dropped    */
/* from a building.  Input value must be between 0 and MAX seconds.      */

#include <stdio.h>
#define GRAVITY  9.81     /* gravitational acceleration (meters/seconds) */
#define MAX      60       /* Upper bound on time of fall. */ 

void main( void )                                                                  
{
    double t;             /* elapsed time during fall (s) */        
    double y;             /* distance of fall (m)         */
    double v;             /* final velocity (m/s)         */ 
    
    printf( "\n\n Welcome.\n"
            " Calculate the height from which a grapefruit fell\n"
            " given the number of seconds that it was falling.\n\n" );

    printf( " Input seconds: " );   /* Prompt for the time, in seconds. */
    scanf( "%lg", &t );             /* keyboard input for time */          

    if (t < 0) {                    /* check for negative input */
        printf( " Error: time must be positive.\n\n" );
    }
    else if (t > MAX) {             /* Is time value too big?     */
        printf( " Error: time must be <= %i seconds.\n\n", MAX );
    }
    else { /* Input is valid; calculate distance and velocity of the fall */
        y = .5 * GRAVITY * t * t;   /* calculate distance of the fall */
        v = GRAVITY * t;            /* velocity of grapefruit at impact */ 
        printf( "    Time of fall = %g seconds \n", t );
        printf( "    Distance of fall = %g meters\n", y );        
        printf( "    Velocity of the object = %g m/s \n", v );
    }

    puts( " Normal termination." );
}