2. What is energy?
Energy is the capacity of an
object or body to transform
an energy source into work.
The quantity of energy is
the equivalent of the quantity
of work.
3. Units of energy
• The international System (IS)
measures energy in joules (J) and
kilojoules.
1000 J = 1 KJ
• Heat energy is often measured in units
called calories (cal) and Kilocalories
(kcal).
1 cal = 4,18 J
5. Muscle energy
Years ago, muscle energy was the main source of energy, but we have
invented different mechanisms and machines that have improved our
quality of life.
For example:
★ Bicycles need our muscle energy when we move the pedals.
★ Kitchen appliances need electricity to work, as televisions and
computers.
14. t
W is work,
measured in
joules (J)
t is time,
measured in
seconds (s)
P= W
P is power,
measured
in watts
(W)
The power of a machine is the quantity of work it
can do per unit of time. Power is expressed in the
formula:
15. Transformation of energy
It’s when we transform
an initial form of energy
into other forms of
energy.
Examples: Chemical to
electrical energy,
luminous to electrical
17. What is?
Energy sources are natural resources that provide
different forms of energy. This energy is transformed
for specific uses. They are classified into:
● renewable sources
● non-renewable sources
