Pressure in fluids

This question is about pressure.

Small air bubbles form in a container of water.

The pressure of the water acts on these bubbles.

The diagrams show the forces that cause this pressure.

Which diagram correctly shows how the pressure of the water acts on a stationary air bubble?

The diagram shows the air bubbles rising to the surface of the water in a container.

Explain why the bubbles increase in volume as they get nearer to the surface of the water.

Assume that the temperature of the water is the same throughout the container.

The teacher pushes the balloon onto the board of nails. The balloon does not pop.

The teacher then pops the balloon using a single nail.

Explain why the balloon does not pop when pushed onto the board of nails.

The diagram shows a submarine at rest underwater.

There are two vertical forces acting on the submarine.

One of the forces is called upthrust.

Give the name of the other force.

Draw two arrows on the diagram to represent the vertical forces acting on the submarine.

State the formula linking pressure, density, gravitational field strength and height.

Calculate the pressure from the water at a point 38 m below the surface of the water.

[density of sea water = 1030 kg/m³]

To rise back to the surface, air is pumped into a storage tank inside the submarine.

Explain how the air exerts pressure on the walls of the storage tank.

The air in the storage tank starts at a pressure of 410 kPa.

As the submarine rises, the air in the storage tank increases in temperature from 2.5C to 18C. The volume of the storage tank remains constant.

Calculate the pressure of the air in the storage tank at 18C.

This question is about air pressure.

During an aeroplane flight, a passenger drinks some water from a plastic bottle.

The air pressure outside the bottle is 80 kPa.

State the air pressure inside the bottle just after the bottle has been sealed.

As the aeroplane descends, the air pressure inside the aeroplane changes.

When the aeroplane lands, the passenger notices that the plastic bottle has collapsed, as shown in diagram 2.

Explain why the bottle has collapsed.

Explain how gas molecules in the air exert a pressure on the surface of the bottle.

This question is about gas pressure.

Diagram 1 shows some of the molecules of a gas in a sealed container.

Diagram 1

The molecules collide with all the surfaces of the container. This exerts an outward force on the container and causes pressure.

Describe how the motion of the gas molecules causes an equal pressure on all the walls of the container.

You may add to diagram 1 to help your answer.

The width of the container is slowly decreased so that the volume of the container is smaller than before.

Diagram 2 shows the width of the container before and after this change. All other dimensions of the container remain the same.

Diagram 2

The initial volume of the gas is 130 cm³.

The initial pressure of the gas is 100 kPa.

Calculate the pressure of the gas after the width of the container is decreased.

Assume the temperature of the gas remains constant.

The diagram shows a simple barometer designed to measure atmospheric pressure.

State the formula linking pressure difference, height, density and gravitational field strength, g.

The total pressure at point X is 117 kPa.

The pressure of the trapped gas is 12 kPa.

Calculate the height of the liquid above point X.

[density of liquid = 1.36 × 10⁴kg/m³]

The Sun shines onto the barometer, increasing the temperature of the trapped gas.

The volume of the trapped gas remains constant.

Explain why the pressure of the trapped gas increases as its temperature increases.

The temperature of the trapped gas increases from 23 °C to 38 °C.

The pressure of the trapped gas is 12 kPa when its temperature is 23 °C.

Calculate the pressure of the trapped gas when its temperature is 38 °C.

The drawing shows a camel and a person in a desert.

Describe a method you could use to find the pressure a person exerts on the ground when standing on two feet.

The total area of contact of the camel’s feet with the ground is 1300 cm².

The mass of the camel is 660 kg.

Calculate the pressure this camel exerts on the ground.

pressure =_........ N / cm²

A manometer is a device that can be used to measure the pressure difference between gas from a gas tap and the atmosphere.

When a gas tap is connected to the manometer, the liquid in the manometer moves due to the additional pressure of the gas.

Before connecting gas tap After connecting gas tap

The pressure difference is linked to the difference in height of the two surfaces of the liquid by the formula

pressure difference = density × g × height difference

The height difference between the two surfaces is 0.094 m.

Calculate the pressure difference between the gas from the gas tap and the atmosphere.

[for liquid, density = 14 000 kg / m³]

The graph shows how the velocity of the surface of the liquid changes with time from when the gas tap is opened to when the water level stops moving.

Use the graph to show that the distance travelled by the surface of the liquid is 4.7 cm.

Calculate the acceleration of the surface of the liquid.

acceleration =_........ cm / s²

Explain how the gas pressure changes if the temperature of the gas increases.

You should use ideas about particles in your answer.

A dam is a structure designed to hold water in a reservoir.

The water in the reservoir has a depth of 35 m.

State the formula linking pressure difference, height, density and g.

Atmospheric pressure at the surface of the reservoir is 100 kPa.

Calculate the total pressure at the bottom of the reservoir.

[for water, density = 1000 kg / m³]

An underwater camera is used in the water reservoir.

The camera lens experiences a force of 430 N at a pressure of 260 kPa.

State the formula linking pressure, force and area.

Calculate the area of the camera lens.

Give a suitable unit.

Sea water has a density of 1030 kg / m³.

Explain how the design of the dam would need to be changed to hold the same depth of sea water safely.

The diagram shows a balloon with a mass attached held at rest just below the surface of a deep pool of water.

The balloon and mass are released.

The graph shows the velocity-time graph for the balloon and mass as they fall through the water.

Use information from the graph to determine the terminal velocity of the balloon and mass.

Explain how the balloon reaches terminal velocity.

You should use ideas about forces acting on the balloon in your answer.

State the formula linking pressure difference, height, density and gravitational field strength.

Calculate the increase in pressure on the balloon when it has reached a depth of 25 m in the water.

[for water, density = 1000 kg/m³]

At the surface, the atmospheric pressure on the balloon is 1.010⁵Pa.

Show that the total pressure on the balloon at a depth of 25 m is 3.510⁵Pa.

At the surface, where the pressure is 1.010⁵Pa, the balloon has a volume of 0.46 m³.

Calculate the volume of the balloon at a depth of 25 m.

Diagram 1 shows an ice cube floating at rest in a beaker of water.

State the value of the resultant force on the ice cube.

Diagram 2 shows the ice cube pushed down into the water by force X.

The ice cube is at rest in this new position.

State the formula linking pressure difference, height, density and gravitational field strength.

The bottom of the ice cube is 0.041 m below the surface of the water.

The density of water is 1000 kg/m³.

Show that the pressure difference between the bottom of the ice cube and the surface of the water is about 400 Pa.

State the formula linking pressure, force and area.

The area of the base of the ice cube is 0.0017 m².

Calculate the upward force on the bottom of the cube from the water due to the pressure difference.

Explain why the ice cube will accelerate upwards when force X is removed.

Diagram 1 shows a plastic bottle containing water.

State the formula linking pressure difference, height, density and gravitational field strength, g.

The pressure difference between the surface of the water and the water at the bottom of the bottle is 2300 Pa.

Calculate the depth of water in the bottle.

Give your answer in cm. [density of water = 1000 kg / m³]

Three holes are made in the bottle at positions A, B and C.

Diagram 2 shows the path of the water leaving the bottle from hole B.

Draw a line on diagram 2 to show the path of the water leaving the bottle from hole A.

Explain the path of the water leaving the bottle from hole A.

Hole C is at the same depth in the bottle as hole B but on the opposite side of the bottle.

Explain the shape of the path of the water leaving the bottle from hole C.

Suggest why there is a hole in the cap of the bottle.

This question is about gas pressure.

The diagram shows a cylinder containing propane gas.

The propane gas is stored in the cylinder at a pressure of 1.03 × 10⁶Pa.

State the formula linking pressure, force and area.

The cylinder has an internal surface area of 1.13 m².

Calculate the force exerted on the walls of the cylinder by the propane gas.

Explain why the pressure exerted by the propane gas acts equally in all directions.

The graph shows how the pressure of a gas varies with its temperature.

Describe how the graph can be used to show that there is a minimum value of temperature, known as absolute zero.

Give the value of absolute zero in °C.

Temperature can also be measured in kelvin.

On the axes below, sketch a graph to show how the pressure of a gas varies with its kelvin temperature.

A glass contains fizzy water.

Bubbles of carbon dioxide form at the bottom of the glass and rise to the surface.

The graph shows the relationship between the volume of a bubble and the pressure of the gas in the bubble.

Describe the relationship shown by the graph.

State the formula linking pressure difference, height, gravitational field strength and density.

The depth of the fizzy water in the glass is 22 cm.

The density of the fizzy water is 1080 kg/m³.

Calculate the pressure difference at the bottom of the glass due to the fizzy water.

Calculate the pressure of the gas in the bubble when the bubble is at the bottom of the glass.

[atmospheric pressure = 101 000 Pa]

When a bubble is at the top of the glass, the pressure of the gas in the bubble is equal to 101 000 Pa and the bubble has a volume of 0.084 cm³.

Calculate the volume of the gas in the bubble when the bubble is at the bottom of the glass.

Assume the temperature of the gas remains constant.

volume =_........ ³

A force called upthrust acts vertically upwards on the bubble.

When the bubble is released, it accelerates vertically upwards.

Draw two labelled arrows on the diagram to show the forces on the bubble as it is released.

A ship floats on the sea.

The ship floats because of the forces acting on it.

The upward force acting on the ship is called upthrust.

This force is shown on the diagram.

Draw another labelled arrow on the diagram to show the other vertical force acting on the ship.

Forces are vector quantities.

State what is meant by the term vector quantity.

Give another example of a vector quantity.

The upthrust force acting on the ship is proportional to the pressure difference between the bottom of the ship and the surface of the sea.

The pressure acting on the ship at the surface of the sea is 100 kPa.

State the formula linking pressure difference, height, density and gravitational field strength (g).

The bottom of the ship is 15.8 m below the surface of the sea.

Show that the pressure acting on the bottom of the ship is approximately 260 kPa.

[density of seawater = 1030 kg/m³]

Explain why the bottom of the ship is deeper below the surface of the sea when the ship is fully loaded with cargo.

A student investigates how much pressure she exerts on the ground when she is standing up.

The weight of the student is 520 N.

State the formula linking weight, mass and gravitational field strength (g).

Calculate the mass of the student.

The student measures the area of one of her feet when it is in contact with the ground.

She draws around her foot on a piece of squared paper.

The squares on the paper have a side length of 2 cm.

Estimate the area of the student’s foot in contact with the ground.

area =_........ ²

State the formula linking pressure, force and area.

The weight of the student is 520 N.

Calculate the pressure the student exerts on the ground when she is standing on both feet.

Give the unit.

The photograph shows a small glass ball used to investigate density and pressure.

The mass of the ball is 19 g.

The density of the ball is 2.3 g/cm³.

State the formula linking density, mass and volume.

Calculate the volume of the ball.

The ball is dropped into deep water and sinks to a depth of 560 cm.

State the formula linking pressure difference, height, density and gravitational field strength.

Calculate the increase in pressure at this depth.

[density of water = 1000 kg/m³]

The density of the liquid is 1.3 x

This is a question about a melting ice cube.

The diagram shows an ice cube placed on the ground.

The mass of the ice cube is 3.7 g and its area of contact with the ground is 2.610^–4 m².

Calculate the pressure the ice cube exerts on the ground.

The ice cube melts and becomes a puddle with a larger cross‑sectional area.

Explain how the pressure of the ice cube on the ground changes when it melts.

Ice melts at a temperature of 0C.

On the axes, sketch how the temperature of the ice cube changes as it rises from a temperature of –10C to a temperature of 20C.

Explain the changes that occur when a solid melts.

Refer to particles in your answer.