Transcript Kinetic and Potential Energy

What is that…
The bowling ball pendulum of death sat suspended
in midair, the tension of the supporting cable
analogous to the tension in the air. Is it art or
science, this bowling ball? What secrets of the
natural world lay trapped inside this bowling ball
pendulum, and how would such secrets become
revealed? And why would anyone in his right
mind suspend a bowling ball from the
ceiling? Surely, this was the work of a
madman.
Introduction to Energy
• For the most part here we will be
concerned with the study of
mechanical energy. By this we mean
that we will be considering the energy
concepts associated with everyday life.
• We are all familiar with energy, so in
your notebook, write down what it is we
mean by energy! (what is energy?)
• How is energy responsible for the
consequences of the bowling ball of
death
The story so far….
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Distance (displacement) is change in position (m)
Velocity is change in position with time (m/s)
Acceleration is change in velocity with time (m/s2)
Mass is a measure of how much matter (kg)
Force is needed to accelerate an object (N)
Momentum is a measure of inertia in motion (kgm/s)
Force x time changes momentum (impulse)
• Next concept is Energy and Work.
Kinetic and Potential
Energy
Objectives
• You will be able to define and identify
Kinetic and Potential energy.
• You will be able to calculate kinetic and
potential energy.
• You will be able to give examples of the
two forms of energy.
• You will be able to explain how one can
transfer to the other.
Objectives continued…
• You will be able to define and calculate
work.
• Describe what determines the power
output of a system.
• Apply the law of conservation of energy
to explain the motion of an object.
Vocabulary terms, you may know
now…you will know later!
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Energy
Joule
Potential Energy
Kinetic Energy
Law of conservation of energy
Definition of Energy…
The ability or capacity to do work.
Measured by the capability of doing work:
potential energy
or
the conversion of this capability to motion:
kinetic energy.
Potential Energy…
• Energy due to position or stored
energy.
Measure by:
PE= (mass) (gravity) (Height)
Potential energy is calculated by:
The object’s mass, multiplied by the earth’s gravitational pull (10 m/sec
sq), multiplied by the distance the object can fall.
PE = mgh
• m = mass (kg)
• h = height (m)
• g = accel due to
(gravity -10 m/s2)
Examples of Potential Energy:
Stretching a rubber band..
-Stores energy
Water at the top of a waterfall..
-Stores energy
Yo–Yo in held in your hand..
-Stores energy because of position
Drawing a Bow…
-Stores energy because of position
• When the position of an object is
altered it, creates Potential Energy.
• A yo-yo on the table, doesn’t have energy,
but when picked up, it alters its position
and now it has the ability (or potential) to
do work.
• A bow doesn’t have the capacity to do
work, unless it’s held at an elevated
position.
Summary of Potential Energy
• Energy that is stored and
waiting to be used later
Definition of Kinetic Energy…
The energy of motion.
Measured by:
2
KE= ½ (Mass) (Velocity)
Kinetic energy is calculated by one half of the object’s mass,
multiplied by the object’s speed- squared.
Examples of Kinetic Energy…
• Shooting a rubber
band.
• Water falling over
the fall.
• A Yo-Yo in motion.
• Releasing the arrow
from the bow.
Potential Energy Converted
to Kinetic Energy…
When stored energy begins to move,
the object now transfers from
potential energy into kinetic energy.
Standing still
Running
What is Kinetic Energy?
o Energy an object has due
to its motion
o K.E. = .5(mass x speed2)
Summary of What You’ve
Learned..
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Example using a coin:
Holding a coin in you hand, alters the coins
original position.
The coin has potential energy, because it
has ability to do work.
Dropping the coin in the bank, changes the
stored energy into motion.
This transfers the coin’s energy from
potential to kinetic energy.
Follow Up Homework…
• At home, find at least 10
objects.
• You will take these objects
and test to see which has
Potential and Kinetic energy
or both.
• Make a chart or table
similar to the one here to
organizing your data.
• Be creative with the
objects you choose, and
make sure you understand
your results to present to
the class.
Potential
Energy
Kinetic
Energy
Both
Example
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Just 1 more thing
• We have learned
all about Potential
Energy and Kinetic
Energy so far…
• But they fall under
1 big form of
energy…
• Mechanical Energy
What is Mechanical Energy?
o Energy due to a
object’s motion
(kinetic) or position
(potential).
The bowling ball has
mechanical energy.
When the ball strikes
the pins, mechanical
energy is transferred
to the pins!
Examples of Mechanical Energy
Cliff Hanger…(pun intended)
See the Potential Energy!!!
• Still to come..
• Practice calculating
different types of
energy
• Calculating Work
• Understanding and
calculating Power
• Are you more
powerful than a
horse?
The End...