Pressure in a Liquid Flashcards

All 7 cards in this deck

What is the equation for the pressure due to a column of liquid?

$p = h\,\rho\,g$ (height of column $\times$ density of liquid $\times$ gravitational field strength).

In $p = h\rho g$, what are the units of $h$, $\rho$ and $g$?

$h$ in metres (m), $\rho$ in kg/m$^3$, $g$ in N/kg, giving $p$ in pascals (Pa).

What are the steps to calculate the pressure due to a column of liquid?

e.g. depth $2$ m of water, $\rho = 1000$ kg/m$^3$, $g = 10$ N/kg

1. Write the equation: $p = h\rho g$
2. Substitute: $p = 2 \times 1000 \times 10$
3. Answer with unit: $p = 20\,000$ Pa

What are the steps to find the difference in pressure between two depths in a liquid?

e.g. depths $2$ m and $5$ m in water, $\rho = 1000$ kg/m$^3$, $g = 10$ N/kg

1. Find the difference in depth: $5 - 2 = 3$ m
2. Use $p = h\rho g$ with that difference: $3 \times 1000 \times 10$
3. Answer with unit: difference $= 30\,000$ Pa

What happens to the pressure on a submarine as its depth increases, and why?

The pressure increases, because the height of the column of water above it increases, so the weight of water acting on it is greater.

How does the density of a liquid affect the pressure at a given depth in it?

The denser the liquid, the greater the pressure — the column of liquid above the point weighs more.

True or false? The pressure at a point in a liquid depends on the width and shape of the container.

False. It depends only on the depth below the surface, the density of the liquid and $g$.