Download Kinetic and Potential Energy

Kinetic and Potential
Energy
What is Energy?
What does it mean if you have
a lot of energy?
For students it means you can
run around, lift weights and
scream.
If you have energy you can do
things.
What is Energy?
Energy is the ability to do work
This is similar to our every day definition of
energy. You can’t run up the stairs (work)
without energy!
We have lots of types of energy. Can you
name a few?
Definition of
Potential Energy…
 Energy
due to position
or stored energy.
Examples of Potential Energy:
Stretching a rubber band…
(stored mechanical potential energy)
Using uranium for energy…
(nuclear potential energy)
Yo–Yo in held in your hand…
(gravitational potential energy)
Lighting a match… (chemical potential
energy)
Gravitational Potential Energy
Gravitational Potential
Energy is energy due to an
objects height above the
ground


Things that are positioned
higher have greater
potential energy

Heavier things have greater
potential energy.
Stored Mechanical
Potential Energy

Energy that is stored due to being stretched
or compressed is called stored mechanical
potential energy.
A sling shot, bow and arrow and springs all have stored
mechanical potential energy.
Chemical and Nuclear
Potential Energy

Chemical and Nuclear energy is energy that
is stored in the atoms of elements. When you
split an element (nuclear) or combine
elements (chemical), a lot of energy is given
off. The energy is not given off until it is split
or combined, so it is considered to be
STORED ENERGY.
Definition of Kinetic Energy…
The energy of motion.
• This includes heat, light,
sound, electricity and
moving objects.
•The faster an object moves, the
more kinetic energy it has.
•The greater the mass of a moving
object, the more kinetic energy it
has.
Examples of Kinetic Energy…


Shooting a rubber
band.
Electricity powering a
light bulb.

Heat waves.

Beating a drum.

Birds flying.
Heat
• Heat is made when the
particles of a substance
moves. The faster the
particles move, the more heat
energy is created.
• Heat moves between objects
that are touching (called
conduction) and between
objects that are not touching
(radiation and convection)
Electromagnetic Energy
• This spectrum includes radio waves, infrared
rays, visible light, ultraviolet rays, x-rays and
gamma rays. Observe an exploded star at
different wavelengths.
• Light is part of a spectrum of electromagnetic
waves. Light enables people to read, see
flowers, determine colors and much more.
Sound
Everything that moves makes a sound as its
particles slide past one another. The sound
something makes is a type of energy that can
travel toward your ear in the form of sound waves.
Once the sound wave hits your ear, your ear drum
and inner ear senses the vibrations and sends
signals to your brain.
Electric Energy
Electric energy is associated with an electric
charge. Electric charges can be used to do work.
Batteries, which convert chemical energy to
electrical energy, are used to operate you cell
phones and laptops. Electrical energy also
happens in nature, as lightning.
Motion
• The movement of an object from one place to
another is considered motion.
• Because “kinetic energy” is defined as energy of
motion, the faster you move, the more kinetic
energy you have.
• Motion can be described by calculating speed or
acceleration of an object.
The Law of Conservation of
Energy

Energy can’t be created or destroyed.


It can only be changed from one form to another.
If energy seems to “disappear”, then consider that
energy might have been changed to motion,
sound, heat or light.
Energy conversions

All forms of energy can be
converted into other forms.


The sun’s energy through
solar cells can be converted
directly into electricity.
Green plants convert the
sun’s energy (light) into
starches and sugars
(chemical energy).
Potential Energy Converted to
Kinetic Energy…
Energy is always transferring between potential
and kinetic energy.
When stored energy begins to move, the object
now transfers from potential energy into kinetic
energy.
Standing still
Running
What happens
when the cord
is cut?
Potential energy
is converted to
kinetic energy!
Kinetic-Potential Energy
Conversion
Roller coasters work because of the energy that is
built into the system. Initially, the cars are pulled
mechanically up the tallest hill, giving them a great
deal of potential energy. From that point, the
conversion between potential and kinetic energy
powers the cars throughout the entire ride.
Kinetic vs. Potential Energy
At the point of maximum potential energy, the car has
minimum kinetic energy.
Kinetic and potential energy
conversions







Describe the energy
conversions in this picture:
At the top: All PE, no KE
¼ of the way down: 3/4 PE, 1/4 KE
½ way down: 1/2 PE, 1/2 KE
¾ down
1/4 PE, 3/4 KE
At the bottom:
No PE, All KE
Is the sum of KE + PE a
constant?
Ball slows down
Ball speeds up
The End...