A person of height 1.65 m is standing upright. The additional external force required by blood vessel of length 1 cm, diameter 1 mm at feet to balance the pressure compared to similar blood vessel in head is
(Density of blood = $1.1 \times 10^3 \, \text{kg m}^{-3}, \, g = 10 \, \text{ms}^{-2}$)