program free_fall_plot
      write(*,*)'Vx=?'
      read(*,*)vx
      write(*,*)'Vy=?'
      read(*,*)vy
      x=0.0
      y=1.0
      dt=0.0001
      i_dummy=pgopen('/xwin')
      call pgenv(0.0,10.0,0.0,10.0,1,0)
      do while (y>=0)
        ax=0.0
        ay=-9.8
        vx=vx+ax*dt
        vy=vy+ay*dt
        x=x+vx*dt
        y=y+vy*dt
        call pgpt(1,x,y,20)
      end do
      write(*,*)'Distance=',x,';Hight=',y
      call pgclos
      end