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.

sanky-diagram-400x207

You can look at OneNote for a clearer image and explanation!