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US 6368 - Demonstrate knowledge of energy transformations Revision Sheet
The key to passing this test is the formulas which are given to you. These tell you the relationships between various physical quantities.
If you can remember these relationships you can answer all of the questions.
Ek 
1
2
mv 2
Ek is kinetic energy – when something is moving it has kinetic energy. How much is determined by its
mass, m (in kilograms), and the velocity it is doing, v (in m/s). Energy is measured in Joules, J.
E p  mgh
Ep is the potential or stored gravitational energy an object has. How much is determined by its mass,
m (in kilograms), and its height above the ground, h (in meters), and the gravitational acceleration
of the body it is currently above, g (on earth this is 9.8m s-2, on the moon it is much less because
the moon is smaller and has less mass to pull you down). Energy is measured in Joules, J.
When something is falling towards the ground from being higher up, all the stored gravitational energy Ep is
converted into kinetic energy Ek as it falls. If something is sliding on the ground down a hill some of that gravitational
potential energy will instead be converted into heat because of friction between the object and the ground. Things
falling through the atmosphere will have some of the energy converted to heat because of friction between the object
and the air. To calculate the energy lost due to friction take the gravitational potential energy an object had before it
started falling and subtract the kinetic energy it has after it had fallen the entire way. The difference between the two
is energy lost to heat via friction and not therefore turned into kinetic energy.
W  Fd
P
W
t
W = Work = the energy transformed within an object or transferred to or from an object. In this case
work = force x distance. Apply a force for a certain distance and that much work will be done to the
object. Work has the same unit as energy which is Joules, J.
P = power = the rate at which work is done. It is the total energy transformed or transferred divided
by the time it took to do so. The unit is watts. E.g. a 100 watt light bulb uses 100 joules of energy
every second 100/1 =100W.
US 6368 - Demonstrate knowledge of energy transformations Revision Sheet
The key to passing this test is the formulas which are given to you. These tell you the relationships between various physical quantities.
If you can remember these relationships you can answer all of the questions.
Ek  1 2 mv 2
Ek is kinetic energy – when something is moving it has kinetic energy. How much is determined by its
mass, m (in kilograms), and the velocity it is doing, v (in m/s). Energy is measured in Joules, J.
E p  mgh
Ep is the potential or stored gravitational energy an object has. How much is determined by its mass,
m (in kilograms), and its height above the ground, h (in meters), and the gravitational acceleration
of the body it is currently above, g (on earth this is 9.8m s-2, on the moon it is much less because
the moon is smaller and has less mass to pull you down). Energy is measured in Joules, J.
When something is falling towards the ground from being higher up, all the stored gravitational energy Ep is
converted into kinetic energy Ek as it falls. If something is sliding on the ground down a hill some of that gravitational
potential energy will instead be converted into heat because of friction between the object and the ground. Things
falling through the atmosphere will have some of the energy converted to heat because of friction between the object
and the air. To calculate the energy lost due to friction take the gravitational potential energy an object had before it
started falling and subtract the kinetic energy it has after it had fallen the entire way. The difference between the two
is energy lost to heat via friction and not therefore turned into kinetic energy.
W  Fd
P
W
t
W = Work = the energy transformed within an object or transferred to or from an object. In this case
work = force x distance. Apply a force for a certain distance and that much work will be done to the
object. Work has the same unit as energy which is Joules, J.
P = power = the rate at which work is done. It is the total energy transformed or transferred divided
by the time it took to do so. The unit is watts. E.g. a 100 watt light bulb uses 100 joules of energy
every second 100/1 =100W.