- Explain why
(a) The blood pressure in human beings is greater at the feet than at the brain.
(b) Atmospheric pressure at a height of about 6km decreases to nearly half of its value at the sea level, though the height of the atmosphere is more than 100 km.
(c) Hydrostatic pressure is a scalar quantity even though pressure is force divided by area.
Ans.
(a) The height of the blood column is quite large at feet that at the brain.
Consequently, the blood pressure in human beings 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 60 km. After 6 km, the density of air deceases but rather very slowly. This is the reason that at a height of about 6 km, a atmospheric pressure reduces to nearly half of its value at 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 i.e.., direction is not associated with the pressure. Hence, it is a scalar quantity.