pressure y9 physics

Pressure

The force applied per unit area.

Force

A push or pull acting upon an object, measured in newtons (N).

Area

The surface over which a force is applied, measured in square metres (m²).

Pascal (Pa)

The unit of pressure equal to one newton per square metre.

Cross-sectional area

The area of the surface perpendicular to the applied force.

Pressure equation

P = F ÷ A, where P is pressure, F is force, and A is area.

Formula triangle

A visual tool to rearrange the pressure formula easily.

High pressure

Occurs when a force is applied over a small area.

Low pressure

Occurs when a force is spread over a large area.

Gravitational field strength

The force per kilogram due to gravity, usually 9.8 N/kg on Earth.

Density

The mass per unit volume of a substance, measured in kg/m³.

Pressure in liquids

The pressure exerted by a liquid depends on depth, density, and gravity.

Normal force

The force acting at 90 degrees to a surface.

Fluid

A substance that flows, including liquids and gases.

Pressure increase with depth

Pressure in a fluid increases with depth.

Depth

The vertical distance below the surface of a fluid.

Pressure difference formula

P = h × ρ × g.

Height (h) in fluids

The depth of the fluid above a given point.

Density (ρ) in fluids

Mass per unit volume, affecting fluid pressure.

g in pressure formula

Gravitational acceleration, typically 9.8 N/kg on Earth.

Force from pressure

Force is pressure multiplied by area (F = P × A).

Unit conversion: kPa to Pa

1 kilopascal (kPa) = 1000 pascals (Pa).

Effect of small surface area

Smaller area increases pressure for the same force.

Effect of large surface area

Larger area decreases pressure for the same force.

Pressure and force relationship

Increasing force increases pressure if area is constant.

Pressure and area relationship

Increasing area decreases pressure if force is constant.

Significant figures

Number of digits used to express precision in answers.

Unit consistency

All quantities must have compatible units in calculations.

Normal pressure in fluids

Acts evenly and in all directions on surfaces.

Pressure in stationary fluids

Pressure is transmitted equally throughout the fluid.

Surface pressure

Force distributed over a given surface area.

kN (kilonewton)

A unit of force equal to 1000 newtons.

Weight

The force of gravity acting on an object's mass.

Pressure at fluid surface

Lower pressure compared to deeper levels.

Pressure at depth

Depends on fluid density, gravitational strength, and depth.

Pascal's principle

Pressure applied to a confined fluid is transmitted equally throughout.

Application of pressure in tyres

Larger tyres reduce pressure to prevent sinking.

Application of pressure in nails

Sharp nails create high pressure to penetrate materials.

Force unit

Newton (N), the SI unit of force.

Area unit

Square metre (m²), the SI unit of area.

Pressure unit

Pascal (Pa), the SI unit of pressure.

Calculating force from pressure

Multiply pressure by area (F = P × A).

Calculating area from force and pressure

Area = Force ÷ Pressure.

Calculating pressure from force and area

Pressure = Force ÷ Area.

Effect of density on pressure

Higher density fluids exert greater pressure at the same depth.

Effect of gravity on pressure

Stronger gravity increases fluid pressure.

Pressure in gases

Gases exert pressure in all directions like liquids.

Worked calculation steps

List knowns, select formula, rearrange, substitute, solve.

Importance of depth in fluids

Deeper points experience greater pressure.

Pressure and submerged objects

Objects experience forces due to fluid pressure on their surfaces.

Unit of gravitational field strength

Newtons per kilogram (N/kg).

Unit of density

Kilograms per cubic metre (kg/m³).

Surface area and pressure relationship

Reducing surface area increases pressure for the same force.