Transcript Energy

Warm Up
•
•
•
•
•
1. What is energy?
2. What is chlorophyll?
3. What is ecology?
4. What is cellular respiration?
5. How does a plant get fertilized?
Energy
Energy Conservation
**Energy is a conserved quantity.
**This provides powerful constraints on
what can and cannot happen in nature.
This is an extremely important concept, and we will come
back to this over and over throughout the remainder of the
course.
What is Energy
Energy: The capacity for doing work (or to
produce heat)
What are some forms/types of energy?
1. Mechanical (kinetic and potential energy)
2. Heat
3. Electricity
4. Electromagnetic waves
5. Sound
6. Nuclear
7. Chemical
8. Mass
• The thing about energy is
that it cannot be created or
destroyed, it can only be
transformed from one form
into another
***Kinetic Energy – Energy of Motion
Kinetic energy (KE) refers to the energy associated
with the motion of an object. The kinetic energy is
simply:
KE = (½)mv2
where
m = mass in [kg],
and
v = velocity of object in [m/sec]
What are the units of KE?
[KE] = [mass] [velocity]2 = [kg*m2/s2] == [Joule]
or just, [J]
A Joule is a substantial amount of energy!
Potential Energy- stored energy
• An object can store energy as the
result of its position.
• Examples: gravitational PE, elastic
PE,
– For example, the heavy ball of a demolition
machine is storing energy when it is held at
an elevated position. This stored energy of
position is referred to as potential energy.
Gravitational PE
• PE related to an objects height.
– GPE=Weight X Height
• Greater the weight, or height, the
more GPE the object has.
Chemical
Energy
 PE
stored in the chemical bonds that
hold chemical compounds together.
Stored in the foods we eat (calories),
matches you use to light a candle, and
even the cells in your body.
Nuclear
Energy
 PE
stored in the nucleus of an atom.
Nuclear energy is released during a
nuclear reaction
For example, nuclear fission, that
occurs when a nucleus splits.
Nuclear power plants use fission
reactions to produce electricity.
Mass Energy
According to Einstein’s Theory of
Special Relativity,
Mass is a form of Energy,
and they are related by the simple and
well-known formula:
E = mc2
M=Mass
C= Speed of light
C = 3.0 X 10^8 m/s
2
E=mc
 The important point here is that energy
and mass are really equivalent, and are
related to one another by simply the speed
of light (c) squared!
 This equation implies that even if a
particle is at rest, it in fact does have a
“rest-mass energy” given by this formula.
Can energy change from one type
of energy to another?
• Nuclear
• Chemical (photosynthesis)
• Kinetic
• Thermal (maintain body temp)
Electrical ( brain/nervous system)
Chemical
(gas)
Electric
(engine)
Sound
Mechanical
Thermal
Electromagnetic
Solar
Electromagnetic
(light, microwave)
Thermal
Chemical (oil)
Kinetic
Electrical
Nuclear
Sound (radio)
Electricity
 Electricity
generally refers to the
flow of charges.
 In most cases, electrons are the
charges which are actually moving.
 Charges are made to flow by applying a
voltage
 Batteries
 Power Supplies
 Electrical generators