Explain why
(a) The blood pressure in humans is greater at the feet than at the brain
(b) Atmospheric pressure at a height of about 6 km 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.
Answers
(a) The height of the blood column in the human body is more at feet than at the brain. That is why, the blood exerts more pressure at the feet than at the brain.
(Pressure = h ρ g where h = height, ρ = density of liquid and g = accleration due to gravity)
(b) Density of air is the maximum near the sea level. Density of air decreases with increase in height from the surface. At a height of about 6 km, density decreases to nearly half of its value at the sea level. Atmospheric pressure is proportional to density. Hence, at a height of 6 km from the surface, it decreases to nearly half of its value at the sea level.
(c) When force is applied on a liquid, the pressure in the liquid is transmitted in all directions. Hence, hydrostatic pressure does not have a fixed direction and it is a scalar physical quantity
Answer:
(a) we know,
P =dgh where, h is dpeth , g is accⁿ due to gravity and d is density of liquid .
Therefore , pressure increases, when depth increases . so, the blood pressure in humans is greater at the feet than the brain .
(B) The density of air is maximum at the surface of the earth and decrease rapidly with height. At height of 6 km , the density of air decreases nearly half of its value at the sea level. Beyond 6km height , the density of air decreases very slowly with height .hence, the atmosphere pressure at the height of about 6km decreases to nearly half of its value at the sea level .
(c) according to Pascal's law,
Pressure is transmitted equally in all directions inside the liquid. it means hydraulic pressure has no fixed direction . so, it's scalar quantity.: