Revision
Remember energy is the ability to do work. It is
measured in Nm or Joules.
We know that to do more work we require more
energy, but we can use various types of energy to
do this work for us.
Other forms of energy
Energy comes in several different forms, but the
ones we shall deal with in this course are:
Kinetic Energy
Kinetic Energy is the energy of movement. It is the
name given to the energy a body possesses due to
its motion.
Calculating Kinetic Energy
The kinetic energy of a moving object is dependent
on two factors: the mass, m, of the object (in kg)
and its velocity, v (in m/s).
Ek = ½ mv2
Potential Energy
Potential Energy can be best thought of as energy stored in a static
object. It can be due to how high the object is above a datum
(starting point), or due to the fact that work has already been done
on the object and energy is stored in it (for example a spring).
Calculating Potential Energy
Ep = mgh
Where m is the mass of the object, g is the acceleration
of gravity acting on the object and h is the height the
object is above the ground or datum.
Electrical Energy
Electrical Energy is the energy provided by electricity It is
one of the most convenient and commonly used forms of
energy since it can be transported easily from place to place
and can be easily changed into other forms of energy.
Calculating Electrical Energy
Ee = ItV
Where V is the voltage of the circuit, I is the
current flowing through the circuit and t is the time
(in seconds) that the circuit has been operating.
Heat Energy
Heat Energy is the energy transferred to a body that results
in a change in the body’s temperature.
Calculating Heat Energy
Eh = mcΔT
Where m is the mass of the material, in kg, ΔT, is the change
in temperature, in degrees (Celsius or Kelvin) and c is the
specific heat capacity of the material being heated.
The specific heat capacity of a substance is the amount of
energy required to raise the temperature of the material by
1K.
Other Forms of Energy
– copy this into your notes
Summary
Kinetic Energy is the energy of movement. It is the
name given to the energy a body possesses due to its
motion.
Ek (Joules)= ½ m(kg) x v2 (velocity)
Potential Energy can be best thought of as energy stored
in a static object. It can be due to how high the object is
above a datum (starting point), or due to the fact that work
has already been done on the object and energy is stored
in it (for example a spring).
Ep(Joules) = m(kg) x g (9.81m/s2) x h
(height)
Other Forms of Energy
– copy this into your notes
Summary
Electrical Energy is the energy provided by
electricity. It is one of the most convenient and
commonly used forms of energy since it can be
transported easily from place to place and can be
easily changed into other forms of energy.
Ee (Joules) = I (current in Amps) x t (secs) x V (voltage)
Heat Energy is the energy transferred to a body that
results in a change in the body’s temperature.
Eh (Joules) = m (kg) x c xΔT (°C or K)
Kelvin & Celsius
The Kelvin is the SI (International System of Units) unit of
temperature. The Kelvin scale is defined by a specific
relationship between the pressure of gas and the
temperature.
This says that “the pressure of the gas is directly
proportional to the temperature in Kelvin”. This means that
Kelvin is an absolute temperature scale, and scientists use
this scale more than any other.
To convert a temperature originally expressed in degrees
Celsius into Kelvins you must add 273.15 units. E.g. O°C is
273.15 K.
Gravity
Objects that have mass pull on each other. We call
this ‘pull’ gravity. The strength of the pull between
two objects depends on two things.
The first is the mass of both of the objects. The
larger the masses the stronger the pull of gravity.
The second is the distance between the two objects.
The larger the distance the weaker the pull of gravity.
Both of the objects will feel this pull of gravity
equally.