Download ME, PE, and KE - Kleins

Take a worksheet!
Do Now!
Mechanical Energy, Potential
Energy, and Kinetic Energy
Mechanical Energy
•
Mechanical energy is the
the energy that enables
something to do work.
•
Energy like work is also
measured in joules
Mechanical Energy
•
There are two forms of
mechanical energy we
need to understand
•
Potential Energy -energy due to the
position of something
•
Kinetic Energy -- energy
due to the movement of
something
Potential Energy
•
Objects can store energy
based on their position
•
This can be thought of as
energy of readiness
•
This is because the
object has the potential
to do work.
Gravitational Potential Energy
•
We know that if we move
an object upwards then
we have done work.
•
Relatively if an object is
moved down because of
gravity work will also be
done.
Gravitational Potential Energy
•
Gravitational Potential
Energy is the energy that
something could have if it
is moved by the force of
gravity.
•
gravitational potential
energy = weight (in
newtons) x height (in
meters)
•
PE = (m)(g)(h)
Try it!
•
Mac and Tosh are
playing on on the porch
of their house. Mac gets
pushed of the porch by
Tosh because he is not
paying attention. Mac
has a mass of 75 kg.
The distance from the
porch to ground is 3
meters.
•
What is the potential
energy of Mac right
before the fall?
Try it!
•
Mac and Tosh are
playing on on the porch
of their house. Mac gets
pushed of the porch by
Tosh because he is not
paying attention. Mac
has a mass of 75 kg.
The distance from the
porch to ground is 3
meters.
•
What is the amount of
work done by Mac
falling?
Try it!
•
Mac and Tosh are
playing on on the porch
of their house. Mac gets
pushed of the porch by
Tosh because he is not
paying attention. Mac
has a mass of 75 kg.
The distance from the
porch to ground is 3
meters.
•
If it takes Mac 1.2
seconds to fall 3 meters
what was the power of
Grab a Worksheet!
Kinetic Energy
•
We already know that
Kinetic energy is energy
of motion
•
What does that mean?
•
What would energy of
motion require?
Kinetic Energy
•
Kinetic energy requires
motion
•
In order to be in motion
we must have a velocity
and object that is moving
•
Therefore, the Kinetic
energy formula uses both
mass and velocity
Kinetic Energy
•
The kinetic energy of a
moving object is always
equal to the work
required to bring it to that
speed from rest.
•
Net Force x Distance =
Kinetic Energy
Work-Energy Theorem
•
We know that there is a
relationship between
work and energy
•
We can say that work will
change kinetic energy
•
If no change in energy
occurs then no work is
done
•
This is also true for
potential energy
Conservation of Energy
•
Now that we know what
energy is, we need to
understand how it
behaves, how it
transforms.
•
In order to look at this we
need to analyze energy
as a transformation from
one form to another
Conservation of energy
•
If you launch a marble
from a sling shot and hit
a fence, we know that the
potential energy of the
rubber band will equal
the kinetic energy of the
marble.
•
If the marble hits a fence
it delivers its kinetic
energy to the fence post.
•
The work done on the
post should equal the
force of impact x the
Conservation of Energy
•
The work done on the
fence however does not
equal the energy from
the marble.
•
This is because some of
the energy is transformed
into heat from the impact.
•
The amount of energy
used to heat the fence
equals the amount of
energy difference
between the marble and
Entropy Slayer 2000
•
Entropy Slayer 2000,
Heated Slingshot
Law of conservation of
Energy
•
Energy can not be
created or destroyed. It
can be transformed from
one form into another,
but the total amount of
energy never changes.