2 Work, Energy and Power Flashcards
Work Formula
Work done = force x distance moved in direction of force
W = F x d
Work SI Units
Joules (J)
Work done is equal to …
the energy transformed
An object may have energy due to …
its motion (kinetic energy) or its position (potential energy)
An object’s energy can be …
transferred and stored
Kinetic energy
Energy that is due to motion
Potential energy
Energy which an object has because of its changed position, shape or state
Gravitational potential energy
The energy stored in objects raised above Earth’s surface, which is due to Earth’s gravitational field
Elastic potential energy
The energy stored when an object is being stretched or compressed
Chemical potential energy
The energy stored by chemical bonds between atoms
Electrical potential energy
In circuits, the current is a flow of electrons, which can transfer energy from, for example, a battery to a light bulb: they have electrical potential energy
Nuclear potential energy
The energy stored in the nucleus of an atom
Thermal energy
When hot objects cool down, their atoms and molecules slow down and lose energy: this is thermal energy
Radiated energy
Light and sound waves are radiated from sources, these carry energy
Kinetic energy formula
KE = ½mv 2
Gravitational potential energy formula
GPE = mgh
Internal energy
The sum of the kinetic and chemical energy of the particles that make up an object
Energy is transferred by … (4)
forces (mechanical working), electric currents (electrical working), heating and waves
Law of conservation of energy
Energy cannot be made or destroyed, but can change from one form to another.
Efficiency equations (3)
Efficiency = useful work done / total energy input
Efficiency = useful energy output / total energy input
Efficiency = useful power output / total power input
Force SI units
Newtons (N)
Energy SI units
Joules (J)
Mass SI units
Kilograms (kg)
Weight is a …
Therefore, its SI units are …
force
Newtons (N)
Average speed equation
Average speed = distance moved / time taken
Acceleration equation
Acceleration = gain in speed / time taken
Force equation
Force = mass x acceleration
Weight equation
Weight = mass x gravity (10N/kg)
W = m x g
Power Equation
Power = work done (energy transformed) / time taken
P = ΔE / t
Renewable Energy Sources (List: 7)
Hydroelectric energy, Tidal energy, Wind energy, Wave energy, Geothermal energy, Solar energy, Biofuels
Non-Renewable Energy Sources (List: 2)
Fossil fuels, Nuclear fuels
Hydroelectric energy
Water flows down from behind a dam, turning generators
Tidal energy
Generators are turned by the tide of water coming in and/or going out
Wind energy
Generators are driven by wind turbines
Wave energy
Generators are driven by the up-and-down motion of waves at sea
Geothermal energy
Means “heat from the Earth” - due to rising steam from water that is pumped down to hot rocks deep underground
Solar energy
Solar panels or solar cells absorb the light energy from the sun and use it to heat water or generate an electric current, respectively
Biofuels
Fuels made from plant or animal matter, sometimes called biomass, which can be burnt to release energy
Fossil fuels
Fuels made from the fossils of plants and animals long ago, which can be burnt to release energy
Nuclear fuels
The energy is released by fission, a process in which the nuclei of uranium atoms are split, at nuclear power stations
The SUN is the source of energy of all of our energy sources except …
geothermal, nuclear and tidal
The MOON is the source of energy for which energy source?
Tidal
Energy is released by what process in the SUN?
Nuclear fusion, a process in which the nuclei of hydrogen atoms are pushed together to form helium
Efficiency can be expressed as a percentage by …
multiplying by 100
