Lesson T3.1.2

T3.1.2 Pressure in liquids and upthrust Quiz: KS3 Physics, Unit 3

20 questions

Written by Revision Ninja · Last reviewed 11 October 2026

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Lesson T3.1.2, Pressure in liquids and upthrust: 20 multiple choice questions for the KS3 Physics (National Curriculum), Unit 3: Pressure, written with Revision Ninja.

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The 20 questions

  1. What does pressure in a liquid increase with?

    • The width of the liquid's surface only, because a wider surface holds more of the liquid's weight
    • Depth below the surface
    • The colour of the liquid, because darker liquids have a greater weight per unit of volume
    • The temperature of the room that the liquid is kept in, because heat makes liquids press harder

  2. In which directions does the pressure in a liquid act at a given depth?

    • Only downwards, because gravity pulls the liquid down and its pressure follows that pull
    • Only upwards, because the liquid pressure lifts everything in it towards the surface
    • Only sideways, because liquid pressure pushes outwards against the walls of its container
    • In all directions at that depth

  3. Why are dams built thicker at the bottom than at the top?

    • Water pressure decreases with depth, so the upper part of the dam needs the greater support.
    • Water is heavier at the top of the dam than at the bottom, so the top must support more.
    • Water pressure increases with depth, so the base must withstand a greater pressure.
    • Dams are only built at the surface of the water, so the thickness at the bottom is for stability.

  4. Why does the water in a deep swimming pool press harder on a swimmer's ears than shallow water does?

    • Water gets warmer at greater depths, and warmth makes the water push harder on the swimmer.
    • The weight of the water above the swimmer increases with depth.
    • Deep water produces less upthrust than shallow water, which leaves the ears under more pressure.
    • Water gets thicker the deeper it is, which makes it press harder on the ears of the swimmer.

  5. A fish is 10 m deep in a lake and another fish is 2 m deep. Which fish experiences the higher pressure?

    • Pressure is higher near the surface than at depth, since the surface takes the greatest load.
    • The fish at 2 m, because surface water is denser than the water found further down the lake.
    • The fish at 10 m, because there is more water above it.
    • They experience the same pressure at any depth, because a fish is protected by its own body.

  6. Which direction does upthrust act in?

    • Downwards from the base of the container, pressing the object into the bottom of the tank
    • Sideways only, pushing the object aside as the fluid moves around it in the container
    • Downwards, from the surface of the fluid onto the top of the object floating in it
    • Upwards, from the fluid onto an object in it

  7. An object floats in water. Which statement is correct?

    • The object's density is always larger than the density of water, which is why it floats upright.
    • The object's volume is always larger than the volume of the water around it, so it floats on top.
    • The object's weight is greater than the upthrust from the water, which keeps it on the surface.
    • The upthrust from the water is equal to the object's weight.

  8. A small block sinks in water. Which statement is true?

    • Its weight is greater than the upthrust acting on it.
    • Its weight decreases as it sinks further down into the water, which is why it keeps going down.
    • The block has no upthrust acting on it at all, because only floating objects feel any upthrust.
    • The upthrust is greater than its weight, so the block is pushed up towards the surface by the water.

  9. Why does a large steel ship float on the sea?

    • Air above the sea pushes the ship upwards, which holds it on the surface while it floats.
    • Ships are hollow, so they have no weight at all and simply rest on top of the sea water.
    • Its shape pushes aside a large volume of water, so the upthrust equals its weight.
    • Ships are lighter than water, so their weight is always less than the water they displace.

  10. What is the unit of pressure?

    • Kilogram per cubic metre (kg/m³), which is the unit of density for a liquid in a container
    • Pascal (Pa), equal to N/m²
    • Newton-metre (N·m), which is the unit of work done when a force moves an object a distance
    • Metre per second (m/s), which is the unit of speed for a liquid flowing along a pipe or tube

  11. When the depth of a liquid is doubled, what happens to the pressure at the bottom?

    • It increases in direct proportion to the depth, so it roughly doubles.
    • It quadruples, because pressure in a liquid depends on the square of the depth of the liquid.
    • It halves, because deeper liquid is less dense than the liquid found nearer the surface.
    • It stays the same at any depth, because the pressure in a liquid is fixed by its container.

  12. A submarine dives deeper into the sea. What must its hull do?

    • Reduce its own weight below zero, so that the submarine can sink more easily into the sea.
    • Spread the pressure in only one direction, so the hull is pushed evenly along its length.
    • Lose all of its upthrust, so that the submarine can stay level as it descends.
    • Withstand the greater pressure from the surrounding water.

  13. Which statement about upthrust is correct?

    • It is always larger than the weight of the object, so every object in a fluid is pushed up.
    • It acts downwards on an object that is in a fluid, pushing the object towards the base.
    • It acts upwards on an object that is submerged in a fluid.
    • It acts only on objects that are floating on the surface and never on fully submerged objects.

  14. A rock hangs from a spring balance. When it is lowered fully into water, the reading on the balance falls. Why?

    • Upthrust from the water acts upwards on the rock, so the spring carries less of its weight.
    • The spring becomes stronger when it is in water, so it lifts the rock with less force.
    • Water adds extra weight to the rock as it goes in, which makes the spring stretch less far.
    • The rock loses some of its mass when it is submerged, so its weight falls on the spring.

  15. Which factors affect the pressure in a liquid?

    • The depth, the density of the liquid and the gravitational field strength
    • The volume of the container only, because a larger container has more liquid pressing down
    • The shape of the container only, because a tall thin container holds more pressure in it
    • The width of the liquid's surface only, because a wider surface spreads the pressure out evenly

  16. Why does a deep-sea diving suit need to be very strong?

    • The suit must lift the diver upwards against the water, so it needs strength to resist the lift.
    • Pressure at depth is large and acts in all directions on the suit.
    • Sea water only pushes upwards on the diver, so the suit must be strong on its top surface only.
    • There is no pressure in deep sea water, so the suit only needs to protect against the cold.

  17. Two identical containers are filled to the same depth, one with water and one with oil, which is less dense. Which has the higher pressure at the bottom?

    • Oil, because oil is always hotter than water at the same depth, and heat increases pressure.
    • They are exactly equal, because the depth is the same and the density of the liquid does not matter.
    • Oil, because it is less dense than water, and less dense liquids press harder at the bottom.
    • Water, because it is denser than oil at the same depth.

  18. An object weighs 5 N in air and 3 N when it is fully submerged in water. What is the upthrust on the object?

    • 8 N upwards, which is found by adding the weight in air to the reading in water
    • 2 N upwards
    • 3 N downwards, which is the reading in water and points in the wrong direction for upthrust
    • 5 N upwards, which assumes that the upthrust equals the full weight of the object in air

  19. What happens to the upthrust on an object fully submerged in a liquid when it is moved deeper?

    • It increases steadily with depth, because the pressure from below pushes harder as it goes deeper.
    • It reverses and acts downwards, because the liquid below the object pulls it further downwards.
    • It falls to zero at a great depth, because the liquid is too compressed to push the object up.
    • It stays the same, because the volume of liquid displaced does not change.

  20. A plastic bottle is filled with water and sinks. Why?

    • An empty bottle has no weight, so it floats, and the water simply adds weight to a weightless bottle.
    • Filling it with water makes its weight greater than the upthrust acting on it.
    • Water removes all of the upthrust acting on the bottle, so nothing holds it up at all.
    • Filling it with water lowers its weight below the upthrust, which should keep the bottle afloat.

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