Table of Contents
• How is work, power and energy related?
• What is energy?
– 2 types
• Kinetic
• Potential
– 2 types
» Gravitational
» Elastic
Table of Contents
• What are other forms of energy?
1. Chemical energy stored in a substance’s chemical
bonds
2. Electrical energy carried in electrical charges
3. Radiant energy carried in electromagnetic waves,
like light
4. Mechanical energy related to an object’s motion and
position
5. Nuclear energy stored in the nuclei of a substance’s
atoms
6. Thermal energy related to a substance’s
temperature
Work, Power and Energy
• What is WORK?
– Work is done on an object when the object moves in
the same direction that the force was applied.
• Lifting your book bag
• Work= Force (N) x Distance (m)
– 1Nm = 1J
• What is POWER?
– The rate at which work is done.
• Running vs walking with your book bag
• Power= work (J) / time (s)
– 1J/s = 1W
Work, Power, Energy
• Energy: The ability to do work or cause a
change.
– Whenever work is done energy is transferred to
that object.
– Power is the rate at which the energy is
transferred.
• What do YOU think the unit for energy is?
JOULES YAY!
Two Types of Energy
1. Kinetic Energy
2. Potential Energy
Kinetic Energy
• “The moving energy”
Kinetic Energy
• Kinetic Energy increases as mass and velocity
increase
Kinetic Energy
Kinetic Energy
• Velocity is squared
– Would velocity have the same, less or more of a effect than
mass on the kinetic energy of an object?
MORE
Kinetic Energy Example
• 1. Determine the kinetic energy of a 625-kg roller coaster car
that is moving with a speed of 18.3 m/s.
• 2. If the roller coaster car in the above problem were moving
with twice the speed, then what would be its new kinetic
energy?
• An object can have energy even when its not
moving!
– Stored energy based off of the objects shape or
position
Potential Energy
• Energy is stored or held in readiness
– Book on your desk
– Apple hanging from a tree
– Pulling back a rubber band
• If the apple stays in the tree, it will keep the
stored energy due to its height above the ground.
• If the apple falls, that stored energy of position is
converted to energy of motion.
Types of Potential Energy
1. Gravitational Potential Energy (GPE)
2. Elastic Potential Energy
Gravitational Potential Energy (GPE)
• GPE: The potential energy related to an
objects position above earths surface.
– Lifting your book on top of your desk = the work
you did to lift it
• Distance the book was moved: height
• Force you used to lift it: weight
Gravitational Potential Energy (GPE)
• Gravitational Potential Energy increases as
weight and height increase.
Gravitational Potential Energy (GPE)
• To calculate GPE use this equation.
• On Earth the acceleration of gravity is
9.8 m/s2 and has the symbol g (in this equation)
Changing Gravitational Potential
Energy (GPE)
• The Gravitational potential energy of an object
can be increased by increasing the height.
• If the objects are at the same height then
what?
– The object with the larger mass would have more
gravitational pull.
Elastic Potential Energy
• Elastic Potential Energy: potential energy
associated with objects that can be stretched
or compressed.
– Pulling back a rubber band
– Winding up a toy
Elastic Potential Energy
• The rubber band has elastic potential energy
here because it has been stretched and is
storing its energy.
• If you let the rubber band go, it sails across
the room.
– As it flies through the air it has kinetic energy due
to its motion.
Remember this!
• Energy comes in MANY different forms!!!!
Mechanical Energy
• What is Mechanical Energy?
–
– Motion
Mechanical = Potential + Kinetic
Examples
Mechanical
Potential
Kinetic
• If the kinetic energy of a falling apple is 5.2J
and its mechanical energy is 8.7J what is its
potential energy?
Mechanical Energy
Law of Conservation of Energy
Energy can neither be created nor destroyed;
rather, it transforms from one form to another.
• To sum up…
– An object with mechanical energy can do work on
another object!
– The more mechanical energy an object has the
more work it can do!
Potential =
Kinetic
Kinetic =
Potential
Thermal Energy
• All objects are made up of particles called
atoms
molecules
_____ and _________.
• These particles are always in motion.
– What kind of energy would they have?
Kinetic
• These particles are arranged in specific ways in
different objects
– What kind of energy would they have?
 Potential
Thermal Energy
• Total potential and kinetic energy of the
PARTICLES in a object is called Thermal
Energy!
Electrical Energy
• What do you think this is?
– Again this is energy of particles!
– The energy of tiny charged particles called…..
ELECTRONS!!!!
– Lets think of some examples....
Chemical Energy
• Chemical compounds are made up of atoms
_____
molecules
and _________.
• Bonds hold these atoms and molecules
together.
• These bonds have Chemical Energy!!!!
• Chemical energy can be released when these
bonds break!!!
Chemical Energy
• Chemical Potential Energy: energy that is
stored in chemical bonds
• Energy is stored in the bonds that hold carbon
and hydrogen atoms together
– The atoms are released when gas is burned
Nuclear Energy
• Potential or Kinetic?
• Where is the energy stored?
– NUCLEUS!
• When is the energy released?
– NUCLEAR REACTIONS!
• 2 kinds
1. Nuclear Fission
•
Example?
2. Nuclear Fusion
•
Example?
Electromagnetic Energy
• Travels in waves
– Does anyone know what waves are?
– These waves have…
• Electrical properties
• Magnetic properties
Electromagnetic!
• What are some examples that we know of
that use waves to transfer energy?
Mechanical
Thermal
Kinetic
Nuclear
Potential
Electromagnetic
Gravitational
Elastic
Chemical
Electrical
Practice 1
Directions: Choose the best answer for each of the following items.
Questions 1 through 3 are based on the following information:
To determine the best location in a greenhouse to grow seedlings, a gardener
places seedling in various locations. She puts 2 seedlings by a north-facing
window, 2 seedlings by an east-facing window, and 2 in the center of the
greenhouse. The gardener measures the height of each plant every 3 days.
After 2 weeks, the gardener compares the growth of the plants in each location.
1. Identify the gardener’s hypothesis. he rate of a seedling’s growth is affected
by the amount of _______________ energy it is exposed to.
2. Which of the following is a strength of her experimental design?
A. She uses seedlings rather than mature plants.
B. The only variable is the location of the plants.
C. She grows plants both inside and outside the greenhouse.
D. She records her measurements on a spreadsheet.
1.Experiment Description:
1. A gardener is conducting an experiment to determine the best location in a greenhouse for
growing seedlings.
2. She places seedlings in various locations:
1. 2 seedlings by a north-facing window
2. 2 seedlings by an east-facing window
3. 2 seedlings in the center of the greenhouse
3. The gardener measures the height of each plant every 3 days.
4. After 2 weeks, she compares the growth of plants in each location.
2.Objective:
1. The goal is to find out which location results in the best growth for the seedlings.
3.Variables:
1. Independent Variable: The location (north-facing window, east-facing window, or center of the
greenhouse).
2. Dependent Variable: The growth of the seedlings (measured by their height).
4.Data Collection:
1. The gardener records the height of each plant every 3 days.
2. This data will be used to analyze and compare the growth patterns.
5.Analysis:
1. The gardener will examine how the seedlings’ growth differs based on their location.
2. She may calculate averages, compare growth rates, or look for any significant differences.
6.Conclusion:
1. Based on the data, the gardener will determine which location is optimal for seedling growth.
Remember, this experiment aims to provide insights into the impact of different greenhouse locations on
seedling development.