Define — 3 marks
A scuba diver descends deeper into the ocean. As they go down, they experience increasing pressure from the water above them. Understanding pressure in fluids is essential for safe diving practices.
-
(a) Define pressure.
[1 mark]
-
(b) Define the term 'fluid' and give one example from the diving scenario.
[2 marks]
Show mark scheme
- (a) Pressure is force per unit area / P = F/A (accept: the force acting perpendicular to a surface divided by the area of that surface)
- (b) A fluid is a substance that can flow / has no fixed shape / takes the shape of its container (accept: a liquid or gas)
- (b) Example: water / seawater (accept: air in the diving tank)
State — 5 marks
A submarine operates at different depths in the ocean. As it descends, the water pressure increases significantly. The submarine's hull must be designed to withstand these extreme pressures without collapsing. Engineers need to understand how pressure varies with depth to ensure crew safety.
-
(a) State the relationship between pressure and depth in a fluid.
[2 marks]
-
(b) State two factors, other than depth, that affect the pressure exerted by a fluid.
[2 marks]
-
(c) State why the pressure acts equally in all directions at a given point within a fluid.
[1 mark]
Show mark scheme
- (a) Pressure increases with depth / pressure is directly proportional to depth
- (a) As depth increases, pressure increases (or equivalent statement showing positive correlation)
- (b) Density of the fluid
- (b) Gravitational field strength / acceleration due to gravity
- (c) Because fluids can flow / particles in a fluid can move freely in all directions / pressure is transmitted equally throughout the fluid in all directions
Describe — 5 marks
A submarine is exploring the ocean at different depths. The submarine has windows made of reinforced glass that must withstand the pressure from the surrounding water. As the submarine descends deeper, the crew notices the water pressure increases significantly.
-
(a) Describe what happens to the pressure in the water as the submarine descends deeper into the ocean.
[2 marks]
-
(b) Explain why the pressure increases with depth in a fluid using the concept of weight.
[2 marks]
-
(c) The submarine windows are circular. Describe how the direction of the pressure force on the windows acts.
[1 mark]
Show mark scheme
- (a) Pressure increases as depth increases / pressure is greater at greater depths (1 mark)
- (a) The increase in pressure is due to the weight of water above / there is more water above at greater depths (1 mark)
- (b) As depth increases, there is a greater mass/weight of water above (1 mark)
- (b) This greater weight exerts a greater force on the fluid below / pressure = force/area, so greater force means greater pressure (1 mark)
- (c) The pressure force acts perpendicular/at right angles to the window surface / acts inward/toward the centre (1 mark)
Compare — 2 marks
A scuba diver descends into the ocean. At a depth of 10 metres, the pressure is approximately 200 kPa. At a depth of 20 metres, the pressure is approximately 300 kPa.
-
Compare the pressure acting on the diver at 10 metres depth with the pressure acting on the diver at 20 metres depth.
[2 marks]
Show mark scheme
- The pressure at 20 metres is greater than the pressure at 10 metres (or pressure increases with depth)
- The pressure at 20 metres is 100 kPa more than at 10 metres (or difference of 100 kPa / pressure increases by 50% / ratio comparison such as 300:200 or 3:2)
Explain — 2 marks
A deep-sea research submersible descends to a depth of 2000 metres in the ocean. The hull of the submersible must withstand the pressure exerted by the surrounding seawater. As the submersible goes deeper, the crew notices the external pressure increases significantly, which affects the structural stress on the vessel.
-
(a) Explain why the pressure in the seawater increases as the submersible descends deeper.
[1 mark]
-
(b) The density of seawater is approximately 1025 kg/m³. Explain how both the depth and the density of seawater affect the pressure experienced by the submersible hull.
[1 mark]
Show mark scheme
- (a) There is more seawater/greater mass of seawater above the submersible at greater depth, which exerts greater weight/force on the fluid below, causing pressure to increase
- (b) Pressure increases with depth because P = ρgh, so greater depth (h) means greater pressure; pressure also increases with greater density (ρ) of the fluid because denser fluids have greater mass in the same volume, exerting more weight and therefore more pressure
GCSE Perfect