GCSE Physics: Pressure in a fluid

All questions and answers

Read through the full deck, or practise recalling each answer above.

1. What is a fluid?

   Show answer

   A liquid or a gas.

2. In which direction does fluid pressure exert a force on a surface?

   Show answer

   Normal to the surface — at right angles to it.

3. What is the equation for pressure at the surface of a fluid?

   Show answer

   p = F / A (pressure = force normal to a surface ÷ area of that surface).

4. What is the SI unit of pressure?

   Show answer

   The pascal (Pa).

5. In p = F/A, area A is measured in ?.

   Show answer

   metres squared (m²)

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

   Show answer

   p = hρg (pressure = height of column × density of liquid × gravitational field strength).

7. What unit is density measured in?

   Show answer

   Kilograms per metre cubed (kg/m³).

8. What unit is gravitational field strength (g) measured in?

   Show answer

   Newtons per kilogram (N/kg).

9. Why does pressure in a liquid increase with depth?

   Show answer

   A taller column of liquid sits above the point, so the weight of liquid pressing down on it is greater.

10. Why does pressure at a given depth increase with the density of the liquid?

    Show answer

    Denser liquid has more mass in the column above the point, so its weight — and therefore the pressure — is greater.

11. Why does a submerged object experience upthrust?

    Show answer

    Pressure is greater on its bottom surface than on its top surface, so there is a resultant upward force.

12. The resultant upward force on a submerged object caused by the pressure difference between its bottom and top surfaces is called ?.

    Show answer

    upthrust