ENERGY RESOURCES AND ENERGY TRANSFERS
Describing energy transfers involing energy stores
Conservation of energy
Efficiency calculations
Sankey diagrams
Work done calculations
Key info
Gravitation potential energy calculations
Kinetic energy calculations
Power calculations
Links between GPE, KE, and W
Work done = Force x distance (W=Fxd)
Work done (J)/(Nm)
Force (N)
Distance (m)
Rearanging:
Force = work done / distance (F = w.d / d)
Distance = work done / force (d = w.d / F)
Power (w)/(J/s)
Energy transfered (J)
Power = Energy transfered / Time
Time (s)
Rearanging:
Time = Energy transfered / Power (t = E / p)
Energy transfered = Power x time (E = P x t)
mass (kg)
gravity (N/kg)
Gravitation potential energy (J)
height (m)
Gravitation potential energy = mass x gravity x height (GPE = m x g x h)
Rearanging:
gravity = energy / mass x height (g = En / m x h)
height = energy / gravity x mass (h = En / g x m)
mass = energy / height x gravity (m = En / h x g)
mass (kg)
Kinetic energy (J)
Velcity (m/s)
Rearanging
Kinetic energy = 1/2 x mass x velocity^2 (KE = 1/2 x m x v^2)
velocity = √2 x ke / m
mass = 2 x ke / v^2
Total energy input (J)
Uselful energy output (J)
Efficiency = uselful energy output / total energy input x100 (EFF = uselful out / total in x100)
Energy stores: chemical, kinetic, gravitational, elestic, thermal, magnetic, electrostatic, nuclear
Energy transfers: mechanically, electrically, by heating, by radiation (light and sound)
Energy can be transferred usefully, stored or dissipated, but cannot be created or destroyed .
Work done is equal to energy transferred
Describe power as the rate of transfer of energy or the rate of doing work
Work done is equal to the change in kinetic energy or gravitational potential energy.
If work is done on an object, its KE or GPE will increase.
Conversely, if work is done by an object, its KE or GPE will decrease.
The energy flow is shown by arrows whose width is proportional to the amount of energy involved.
The wasted and useful energy outputs are shown by different arrows.
You can look at OneNote for a clearer image and explanation!