PHYSICS

Law of Conservation of Energy

energy cannot be created or destroyed, only transformed from one form to another or transferred between objects.

Reason useful energy decreases in real systems

Energy is transformed into non-useful thermal or acoustic energy due to resistive forces like friction and air resistance.

Gravitational potential energy (EpEp​)

The energy stored in an object due to its vertical height above the ground, determined by the formula Ep=mghEp​=mgh.

Kinetic energy (EkEk​)

The energy an object possesses because of its motion, determined by the formula Ek=12mv2Ek​=21​mv2.

Direction of spontaneous heat transfer

Thermal energy always flows naturally from a warmer object to a cooler object until both reach thermal equilibrium.

Conduction

Thermal energy transfer through solids via collisions between adjacent vibrating particles, transmitting kinetic energy.

Convection

Thermal energy transfer in fluids where heated fluid expands, becomes less dense, and rises, while cooler, denser fluid sinks to take its place.

Thermal radiation

Heat transfer via infrared electromagnetic waves that does not require matter and can travel across a vacuum.

Reason temperature remains constant during melting or boiling

Supplied thermal energy is absorbed as latent heat to break attractive intermolecular bonds rather than increasing the particles' kinetic energy.

Particle movement in solids compared to liquids

Solid particles vibrate in fixed positions within a rigid structure, whereas liquid particles have higher kinetic energy and can slide past each other.

Power (PP)

The rate at which energy is transferred or transformed over time, calculated using P=EtP=tE​ and measured in watts (WW).

Efficiency

A measure of the proportion of total input energy that is successfully converted into useful output energy rather than wasted.

Standard unit conversions for mass, distance, and time

Divide grams by 10001000 to obtain kilograms, divide centimetres by 100100 to obtain metres, and multiply minutes by 6060 to obtain seconds.