NOTES
SEPTEMBER 2020
Chapter 15 : ENERGY
GRADE: 6
SUBJECT: PHYSICS
1) Definition of Energy?
Answer: It’s able to exert a force and to do work. Energy is also define as capacity to do work
2) How you measure energy?
Answer: Quantities of energy given in one unit can always be converted to any other unit of energy.
For example, 1 gram calorie is equivalent to 4.186 joules, which is used to measure heat energy.
The Law of Conservation of Energy:
 Energy can be neither created nor destroyed.It can only be converted from one form to
another.
3) Types of energy
i) Gravitational potential energy: Gravitational potential energy is energy an object possesses
because of its position in a gravitational field.

The formula to find Gravitational potential energy is
Gravitational potential energy = Weight X Height.
ii) Strain energy: Whenever you push or pull on a deformable object like a rubber band or spring, you
transfer some energy to it.
iii) Chemical energy: The chemical energy is stored in the links between the atoms. Fuel and food
are forms of stored chemical energy.
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2020
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iv) Kinetic energy: The ability to do work, so all moving things have energy by virtue of their motion.
This type of energy is called kinetic energy. Kinetic energy depends on both mass and velocity.

If mass or velocity increases kinetic energy increases if mass or velocity decreases kinetic energy
decreases because mass & velocity is directly proportional to kinetic energy.
v) Sound energy: Sound energy is the form of energy generated when an object vibrates. Once
produced through vibrations, sound energy is transferred in waves through mediums such as air and
water before it reaches your ears.
vi) Electrical energy: The energy which is caused by the movement of the electrons from one place
to another such type of energy is called electrical energy
vii) Internal energy: Internal energy or heat energy is defined as the energy associated with the
random, disordered motion of molecules.
viii) Electromagnetic energy: Electromagnetic radiation is energy that is propagated through free
space or through a material medium in the form of electromagnetic waves, such as radio waves,
visible light, and gamma rays. The term also refers to the emission and transmission of such radiant
energy.
ix) Light energy: Light energy is a kind of kinetic energy with the ability to make types of light visible
to human eyes. Light is defined as a form of electromagnetic radiation emitted by hot objects like
lasers, bulbs, and the sun.
The light speed is equal to 186,400 miles (300,000 km) per second.
x) Mechanical energy: Mechanical energy is the energy that is possessed by an object due to its
motion or due to its position. Mechanical energy can be either kinetic energy (energy of motion) or
potential energy (stored energy of position). ... A moving car possesses mechanical energy due to its
motion (kinetic energy).
xi) Wasted energy: Wasted energy is energy that is not usefully transferred or transformed. Energy
cannot be made or destroyed. Energy is transformed into a different form that can be used. When
energy is transformed or transferred only part of it can be usefully transformed or transferred. The
energy that is not used in this process is wasted energy.
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Energy changes: Energy can change from one form to another.
For example:
 Chemical energy might change to heat energy.
 Light energy can change to chemical energy. (For example in the garden there are plants and
flowers growing. Light energy from the sun lands on the leaf. Inside the leaf a chemical
change happens)
Fuels:
Substances are burned to release their chemical energy to provide heat and light. They are called
fuels.
Wood, coal, gas, charcoal, oil, diesel oil, petrol, natural gas and wax are examples of fuels.
Coal, gas and oil were fossil fuels.
Fossil fuels:
A fossil fuel is a fuel formed by natural processes, such as decomposition of buried dead organisms
and plants.
Renewable resources:
Alternative sources of energy formed from renewable energy Sources such as the movement of the
wind, the movement of waves and the tide, the movement of water from rivers
(Hydroelectricity) and the light of the Sun (solar power).
Examples of renewable energy sources are solar energy, wind energy, hydropower
Nonrenewable Resource:
A nonrenewable resource is a natural substance that is not replenished with the speed at which it is
consumed. It is a finite resource. Fossil fuels such as oil, natural gas, and coal are examples
of nonrenewable resources.
Examples of non-renewable energy sources coal, oil, and natural gas.
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