P1 Energy Flashcards
What is energy?
Energy cannot be created nor destroyed - only moved from one store to another.
What are the energy stores?
Chemical
Gravitational
Kinetic
Thermal
Elastic
Electrical/ magnetic
Nuclear
When is energy useful?
Energy is only useful when concentrated.
What is dissipation?
Where energy is transferred to the thermal energy store of the surroundings. This energy is very dilute and hard to make use of.
What is the equation for kinetic energy?
Ek = 0.5xmxv^2
0.5 x mass x velocity squared
Where is kinetic energy stored?
In moving objects.
Where is elastic energy stored?
Elastic energy is stored in stretched or compressed objects.
What is the equation for elastic potential energy?
Ee = 0.5xkxe^2
0.5 x spring constant x extension squared
Where is gravitational potential energy stored?
In climbing/ falling objects.
What is the equation for gravitational potential energy?
Ep = mgh
Mass x gravitational field strength x height
Energy changes template
The _ store decreases as _
The _ store increases as _
Thermal energy is transferred to the surroundings due to friction between moving parts/ electrical resistance.
What is the equation for power?
Energy/ time
What is the equation for efficiency?
Useful power output/ total power input
Useful energy output/ total energy input
What can efficiency not be greater than?
100% or 1.00
What is a closed system?
Energy cannot leave or enter the system. Total energy in the system stays the same.
What are ways to reduce unwanted dissipation?
Lubrication of moving parts using oil
Low resistance wiring
Stream lining reduces air resistance
Insulation in buildings
How do you reduce unwanted dissipation in houses?
Cavity wall insulation (foam)
Loft insulation (fibre glass)
Draft excluder
Double or triple glazed windows
Carpets and underlay
Foil behind radiators
What is work done?
Energy transferred by a force
What is the equation for work done?
Force x distance
What happens when a falling object hits the ground without bouncing back?
It’s kinetic energy store decreases. Some or all of its energy is transferred to the thermal energy store of the surroundings.
What eventually happens to all wasted energy?
It is transferred to heat and dissipated to the surroundings.
What is nuclear energy?
Energy when it is stored inside atoms.
What is chemical energy?
Energy when it is stored in chemical substances such as food, fuel or batteries.
What is energy?
Something that is needed to make things happen or change.
