Physics NCEA L1

Mechanical energy, formulas, thermal energy, electricity

Law of Conservation of Energy

Energy cannot be created or destroyed, only transformed or transferred.

Mass

The amount of matter an object contains.

Weight

The effect of gravity on the mass of an object.

Weight is a force measured in

Newtons (N)

Mass is measured in

kilograms (kg)

Gravitational energy formula

Ep= mgh

Kinetic Energy formula

Ek=1/2mx v squared

Friction

When two surfaces move against each other, causing resistance.

Energy Losses

Any energy that is transformed into an undesired form.

Energy Efficiency

The ratio of useful energy output to total energy input, often expressed as a percentage.

Friction can be reduced by..

using lubrication or smooth surfaces.

Work Formula

W=Fd

Power formula

P=W/t,

Temperature

a measure of the average kinetic energy of particles in a substance.

Thermal Energy

the total energy of all the particles in a substance

Heat

Form of energy transfer due to temperature difference between systems.

Thermal Energy depends on both the

speed of particles and number of particles

During positive heating the temperature

increases

During negative heating the temperature

decreases

Conduction

transfer of thermal energy through direct contact.

Thermal Conductor

Materials with electrons that move easily, transferring energy.

Thermal Insulator

Materials that don’t conduct heat well because they lack free electrons.

Convection

Transfer of thermal energy through the movement of fluids

Fluids

Liquids and Gases

In terms of density, particles further apart means

less dense

In terms of density, particles closer together means

more dense

Radiation

Transfer of energy through electromagnetic waves

When radiation strikes an object energy is either

Absorbed, reflected, or partially absorbed

Liquid

Has no fixed shape but has a fixed volume

Solid

Has a fixed shape and fixed volume

Gas

Has no fixed shape or volume

Latent heat

Heat needed for phase change without temperature change.