program fly_free_plot
      if(pgopen('/xwin')<=0)stop
      call pgenv(0.0,5.0,0.0,5.0,1,0)
 1000 write(*,*)'Initial Vx?'
      read(*,*) vx
      write(*,*)'Initial Vy?'
      read(*,*) vy
      dt = 0.001
      x = 0.0
      y = 1.0
      ax = 0.0
      ay = -9.8
      do while (y >= 0.0)
        x = x + vx*dt
        y = y + vy*dt
        vx = vx + ax*dt
        vy = vy + ay*dt
        call pgpt(1,x,y,20)
      end do
      write(*,*)'Distance is',x,'Hight is',y
      write(*,*)'Again? (0=stop, *any value*=again)'
      read(*,*)i
      if (i==0) stop
      goto 1000
      end