Name:
Activity 1
1) Write down a definition for POTENTIAL energy.
2) Write down a definition for KINETIC energy.
Mechanical Systems
A mechanical system has many parts that all work together to perform a task. Each of
these parts require energy to do what they need to do so that the entire system can
perform its task. There are many energy transfers that take place in systems to make
them work.
The mechanical system can be simple (like a pair of scissors) or complex (like a
bicycle).
Example: Scissors
When the blades of the scissors move together and apart, they are able to cut a piece
of paper.
When you hold the scissors in your hand and move the blades apart, they have
potential energy. When they are moved together, they have kinetic energy and they
can cut through a piece of paper.
INPUT
Scissors held in
hand, open, with
blades apart.
Scissors has
potential energy.
OUTPUT
Scissor blades
move together
and cut through
a piece of paper.
PROCESS
Scissors are
closed so the
blades are
moved together.
Scissors has
kinetic energy.
Potential energy
changes into
kinetic energy.
© e-classroom 2014 www.e-classroom.co.za
GRADE 7
Grade 7 Term 3 Natural Science: Energy and Change: Potential and Kinetic Energy: Potential and Kinetic Energy in Systems 1
Potential and kinetic energy in systems-1
GRADE 7
There are many different parts that work together to make a bicycle move forward.
These parts include: the pedals, front cog and rear cog, chain and wheels.
A person riding a bicycle has potential energy in their body. When they move the
pedals, they move the front cog and chain. The chain moves the rear cog which turns
the wheel. As the wheels turn, they move the bicycle forward. When the bicycle is not
moving, it has potential energy. When the bicycle parts move together they move
the bicycle forward with kinetic energy.
1
INPUT
Bicycle parts are at rest. Person is on the bike, ready
to begin cycling.
Parts have potential energy and so does the person
on the bike.
2
PROCESS
Person begins to pedal. Pedals move the cog and
front cog moves the chain. The chain moves the
rear cog. Together these parts move the wheels.
Potential energy changes into kinetic energy.
3
OUTPUT
Wheels move the bicycle forward.
Bicycle has kinetic energy.
Person’s legs are also moving and have kinetic
energy
Activity 2
Draw an energy flow diagram in your class workbook to show the energy
transfers that take place in a fishing rod.
Fishing rods have a handle attached to the reel. Fishing line is wound onto the reel. As
the fisherman turns the handle, the reel turns which winds up the fishing line onto the reel and reels the fish in from the water.
© e-classroom 2014 www.e-classroom.co.za
Grade 7 Term 3 Natural Science: Energy and Change: Potential and Kinetic Energy: Potential and Kinetic Energy in Systems 1
Example: Bicycle
GRADE 7
Activity 1
1) Write down a definition for POTENTIAL energy.
Potential energy is stored energy, waiting to be released. There are three types: Gravitational, Chemical and Elastic potential energy.
2) Write down a definition for KINETIC energy.
Kinetic energy is movement energy that is used to do work.
Activity 2
Draw a energy flow diagram, in your book, to show the energy transfers that
take place in a fishing rod.
Fishing rods have a handle attached to the reel. Fishing line is wound onto the reel. As the
fisherman turns the handle, the reel turns which winds up the fishing line onto the reel
and reels the fish in from the water.
INPUT
PROCESS
OUTPUT
Fishing rod parts are
at rest. Man is ready
to reel in the line.
Man begins to turn
the handle. Handle
turns the reel.Fishing
line is wound around
the reel.
The parts move
together to reel in
the fishing line and
wind it around the
reel.
Potential energy
changes into kinetic
energy .
Fishing rod, reel and
handle, as well as
the fishing line are
all moving and have
kinetic energy. The
man is also using
kinetic energy to
reel in the line.
Parts have potential
energy and so does
the man holding the
fishing rod.
© e-classroom 2014 www.e-classroom.co.za
Grade 7 Term 3 Natural Science: Energy and Change: Potential and Kinetic Energy: Potential and Kinetic Energy in Systems 1
Answer sheet