$A$ tank $5 \,m$ high is half filled with water and then is filled to the top with oil of density $0.85 \,g/cm^3$. The pressure at the bottom of the tank,due to these liquids is ........ $g/cm^2$.

Equal masses of water and a liquid of density $2 \ g/cm^3$ are mixed together. The density of the resulting mixture is ........ $g/cm^3$.

What is atmospheric pressure?

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 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.

What is atmospheric pressure?

At shallow depth $h$,the pressure in the ocean is simply given by $P = P_0 + \rho gh$,in which $\rho$ is the density of water and $P_0$ is the air pressure. As we go deeper,the high pressure causes the water to compress and become denser. Which of the following sketches illustrates the correct dependence of the pressure on the depth $h$ ?