(a) The height of the blood column is quite large at feet than that at the brain. Consequently, the blood-pressure in humans is greater at the feet than at the brain.
(b) Density of air decreases very rapidly, with increase in height and reduces to nearly half its value at the sea level at a height of about 6 km. After 6 km, the density of air decreases but rather very slowly. This is the reason that at a height of about 6 km, atmospheric pressure reduces to nearly half its value at the sea level.
(c) Force is a vector quantity but pressure is a scalar quantity. According to Pascal's law pressure is transmitted equally in all directions that is, the direction is not associated with the pressure. Hence, it is not a scalar quantity.
