Summary - Potential and Kinetic Energy Grade 7 Natural Sciences
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Course
Natural Sciences
Institution
7th Grade
This document provides a comprehensive summary of potential and kinetic energy in systems. It looks at the difference between potential and kinetic energy with definitions and the different energy systems, including: Mechanical systems, thermal energy, electrical systems and biological systems. Exa...
Potential and kinetic energy in systems
• Renewable and non-renewable sources are where we get our energy FROM.
• Potential energy and kinetic energy are two TYPES of energy.
The difference between potential and kinetic energy
Potential energy
• This picture shows a ramp with a marble rolling down into a foam cup.
• The marble will knock the cup and make it move.
• When the marble is released, it rolls down the ramp and transfers some of
its energy to the cup.
• This transfer of energy is what makes the cup move.
• When you hold the marble at a distance up the ramp, you are preventing it
from rolling down the ramp.
• This means that the marble has the potential to roll down and knock the
cup.
• So, YOU gave the marble POTENTIAL ENERGY by picking it up and
holding it at the top of the ramp.
• When the marble hits the cup, the marble transfers energy to the cup
which then moves.
• The cup then comes to a stop after a while.
• The greater the vertical height of the marble, the further the cup moved.
• This tells us that lifting the marble to a higher position means that it has
more potential energy than if it was released from a lower position.
• So the higher an object is above a surface, the more potential energy it
has.
, • In this diagram, we are looking at a system consisting of: the arm, the brick
and the Earth that pulls on the brick.
• When the brick was on the floor, it had no potential energy, but when it is
lifted up, it has potential energy.
• The potential energy comes from THE BOY who picked up the brick and
held it in the air.
• When the boy lets go of the brick and it falls down to the ground and
makes a hole in the sand, the sand receives the energy of the falling brick.
• The hole in the sand pit will be deeper if we drop the brick from a higher
point.
• The energy is all still there within this system, but it is not easy to use
anymore.
• The sand is warmer but we cannot actually use that energy for anything
because the temperature increase was so small.
• So the energy in the system has not been destroyed, but it is less
available for us to use.
• In this diagram, we are shooting match boxes with elastic bands by
stretching the bands and releasing them to hit the matchbox.
• When the elastic band was stretched it gained potential energy.
• We know this because your hand had to do some work to stretch the
elastic band, and now the elastic band can snap back and move the
matchbox.
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