Transcript Energy - Solon City Schools

Energy
What the heck is energy anyway?
• Energy- the ability to do work
• If an object or organism does work (exerts a
force over a distance to move an object) the
object or organism uses energy.
•
Work = force x distance
ex. When stretching a sling shot, you do work,
and energy is transferred to the sling shot
• Measured in the unit joules (honors Mr. Joule)
• b/c work is a force x distance it is measured in
Newtons x meters. These units are called
joules. Work = force x distance
•
•
1 N x m = 1 J= 1 kg x m2/s2
Energy
• Living organisms need energy for
growth and movement.
• You use energy when you hit a tennis
ball, compress a spring, or lift a
grocery bag.
• Energy is the ability to do work
Nature of Energy
• Energy is all around you!
– You can hear energy as sound.
– You can see energy as light.
– And you can feel it as wind.
Types of Energy
• Mechanical energy- sum of the potential &
kinetic energy in a system
• The amount of work an object can do because of
the object’s kinetic and potential energies
• *** If something has mechanical energy you
can see it move (or you would see it move if
it only has potential energy)
• This type of energy is on a large scale
• ex. Apples have potential energy when they are
hanging above the ground, & they have kinetic &
potential energy when they are falling
•
ex. Roller coaster
Types of Mechanical Energy
• 1. Potential energy- energy that an object has
b/c of its position, shape, or condition of the
object
• Called “energy of position” or “stored
energy”
• Stretched rubber band has potential energy b/c
the 2 ends are far away from each other (elastic
potential energy)
Gravitational potential energy
• Gravitational potential energy- any
system of 2 or more objects separated by
a distance; results from gravitational
attraction b/w the objects
•
ex. Apple in a tree
• Grav. PE = mass x free-fall acc. X height
• PE = mgh
Gravitational Potential Energy
• An apple at the top of the tree has more grav.
PE w/ respect to the Earth than a similar apple
on a lower branch.
• But if two apples of different masses are at
the same height, the heavier apple has more
grav. PE than the lighter one
Types of Mechanical Energy
• 2. Kinetic Energy- energy of a moving object
due to the object’s motion
-depends on mass & speed
Kinetic energy = ½ x mass x speed squared
KE = ½ x mv2
• in the KE equation, speed is squared so a small
increase in speed produces a large increase in
KE
ex. Why car crashes are more dangerous at
high speeds
• Atoms/molecules have KE b/c they are
constantly in motion (KE ↑ as particles heat up
or KE ↓ as particles cool down)
Kinetic Energy
Non-mechanical Energy
• Energy that lies at the level of atoms and does
not affect motion on a large scale
• So, this type of energy is on a small scale and
you cannot see it
• Example: apples give you energy when you eat
them
Nonmechanical Energy
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***Nonmechanical energy can be
Heat energy
Light energy (electromagnetic)
Chemical energy
Nuclear energy.
Electricity
Once again, you CANNOT SEE
nonmechanical energy*
Types of Non-mechanical Energy
• 3. Chemical Energy- The amount of
chemical energy associated w/ a
substance depends in part on the relative
positions of the atoms it contains
• formation of bonds and the breaking of
bonds during chemical reactions
•
ex. Burning a match
• B/c chemical energy depends on
position, it is a kind of potential energy
Chemical Energy
• Energy that exists in the bonds
that hold atoms together.
• When bonds are broken,
chemical energy is released.
• Examples:
• Digesting food…bonds are
broken to release energy for
your body to store and use.
• Sports… your body uses energy
stored in your muscles obtained
from food.
• Fire–a chemical change.
Types of Non-mechanical Energy
• 4. Nuclear Energy- kind of potential
energy stored by the forces holding
subatomic particles together in the nuclei
of atoms
• Nuclear Fusion- a type of reaction in
which light atomic nuclei combine to form
a heavier nucleus
•
ex. How sun works
• Nuclear Fission- a single heavy nucleus
is split into 2 or more lighter nuclei
•
ex. How a nuclear power plant works
•
by the fission of uranium
Types of Non-mechanical Energy
• 5. Electricity- results from the flow of
charged particles through a wire or other
conducting materials
• Lightning is caused by electrons traveling
through the air b/w the ground & a
thundercloud
Electromagnetic Energy
• 6. Electromagnetic Energy
(Light)- travels from the sun to the
Earth across empty space in the
form of electromagnetic waves
• Each color of light (Roy G Biv)
represents a different amount of
electromagnetic energy.
• Electromagnetic Energy is also
carried by X-rays, radio waves, and
laser light.
Types of Energy
• 7. Thermal Energy is the kind of energy that is
related to and/or caused by heat.
• When you boil a pot of water, you are
contributing thermal energy or heat to the
bottom of the pot. This thermal energy is then
transferred to the water inside the pot.
• As the water molecules move faster (kinetic
energy), they begin to get hotter. As they move
faster and faster, each one tries to leap away
from its neighbors and into the surrounding air to
form water vapor, or steam. Once the water
starts boiling, it turns into steam very quickly!
Can mechanical energy change to
non-mechanical energy?
• Yes, as a result of air resistance and
friction.
• Moving an object across another can
result in heat through friction. This is
conversion of the mechanical energy into
thermal energy.
• In an electric motor, the (mechanical)
rotation of the coils results in electrical
current and therefore electrical energy.