(1) Energy Changes in a System Flashcards
Equation for kinetic energy
1/2 x Mass x Velocity ²
( 1/2 mv ² )
Mass= kg Velocity= m/s
Equation for Elastic potential energy
1/2 x Spring constant x (extension)²
( 1/2 ke ² )
Spring constant= N/m Extension= m
Equation for Gravitational potential energy
Mass x gravitational field strength x height
( mgh )
Mass= kg Gravity of earth= 9.8 Height= m
Define specific heat capacity
The amount of energy needed to raise the temperature of 1kg of a substance by 1°C
(Energy transferred= Mass x SHC x temperature change)
State the units for specific heat capacity
J/°C/Kg
Joules/degrees Celsius/Kilograms
State the definition of power
The rate at which energy is transferred (rate at which work is done)
Equation for Power
Power= energy transferred/time
Power= work done/time
Energy and work done= J Time= s
What is the unit of power?
Watt (W)
State 4 different stores of energy
- Kinetic energy
- Gravitational potential energy
- Elastic potential energy
- Chemical energy
- Thermal energy
- Nuclear energy
State 3 different transfers of energy
- Light energy
- Sound energy
- Electric energy
Give examples of chemical energy
- Food
- Fuel
- Batteries
Describe the energy transfers of a bungee jumper
• When falling GPE is converted into KE
• As the cord tightens the KE is converted to EPE
(At the lowest point the jumpers initial GPE equals the EPE stored in the cord)
Describe the energy changes involved when throwing a ball upwards
When thrown up the KE is converted to GPE, then at the peak there is maximum GPE and no KE end then when it falls back down the GPE is converted to KE again.
Define a system
A system is an object or groups of objects
What are the 4 ways energy can be transferred?
• Mechanical work- a force moving an object through a distance
• Electrical work- charges moving due to a potential difference (voltage)
• Heating- due to a temperature difference (caused electrically or chemically)
• Radiation- energy transferred in a wave (eg. Light or infrared)
