Transcript energy - Solon City Schools

Energy Conversion and Conservation
Notes
March 28, 2016
Which of the following is a measure of
the ability to do work?
33%
is
he
s
yn
t
ot
os
Ph
ul
es
0%
Jo
0%
er
gy
4.
En
3.
67%
w
er
2.
Power
Energy
Photosynthesis
Joules
Po
1.
I.) Energy Conversion
A) Energy Conversion
1) Energy can be converted from one form to another.
2) Can take place in a series of steps (Ex: striking a match)
B) Conservation of Energy
1) The law of conservation of energy states that energy
cannot be created or destroyed. (Energy lost = Energy
gained)
2) The amount of energy in the beginning must be same
amount at the end.
a) Example: Riding a bike
1) When you stop pedaling, the bike will
eventually stop.Where does the KE go?
Frictional forces act on the bike and turn KE into
thermal energy
C) Energy Conversions
1) Most common conversion is between
PE and KE
2) The gravitational PE of an object is
converted to the KE of motion as object
falls. (Ex: Avalanche)
3) Energy conversions in Pendulums
a) KE and PE undergo constant conversion in a pendulum
PE is
greatest
PE is
greatest
KE = 0
KE = 0
KE is
greatest
PE = 0
Mechanical vs Nonmechanical Energy
(write somewhere on your notes- no blanks!)
1. Mechanical Energy-
Energy you can “see”
* If something has mechanical
energy you can see it move (or
you would see it move if it only
has potential energy)
Non-mechanical Energyenergy you cannot “see”
 Exs Energy between atoms in a
molecule
 apples give energy when eat them
*Non-mechanical energy can be heat energy,
light energy (electromagnetic), chemical energy,
or nuclear energy.
*Once again, you CANNOT SEE nonmechanical energy
4) Calculations
-Mechanical Energy = sum of the KE + PE in the components of
a mechanical system
-Conservation of Mech. Energy:
(KE + PE)beginning = (KE + PE)end
D) Energy and Mass
E = mc2
1) Einstein’s equation, E=mc2, says that energy and mass are
equivalent and can be converted into each other.
II.) Transfer of Thermal Energy
A) Conduction: the transfer of energy through direct
contact of a material
1) This occurs within a material or between
materials that are touching
2) Conduction in gases is slower than in liquids and
solids because the particles collide less often in a gas
3) Thermal conductor: transfer of heat energy through a
material
a) Examples: -Wire rack in hot oven
- Tile floor
4) Thermal Insulator: material that is a poor conductor
of heat and therefore reduces energy transfer
a) Examples: -Wooden spoon
- Air
- Styrofoam
B) Convection: the movement of matter due to differences in
density that are caused by temperature variations
1) Particles can transfer thermal energy from hot to cold area
2) Example: Oven
-Temp is higher at bottom of the oven
- Air at bottom heats up & is then less dense
-HOT air RISES
- The air that was at the top, cools off & is then more dense
-COLD air SINKS
3) Convection current: the vertical movement of air currents due to
temperature variation
a) Convection currents are important in many natural cycles,
such as ocean currents, weather systems, and movements of hot
rock in Earth’s interior.
C) Radiation: the energy that is transferred as electromagnetic
waves, such as visible light & infrared waves
1) Examples: - Sun
- Standing by grill & feel the heat
- Heat lamp in restaurant
Which of the following does a flying
Frisbee have the most of?
5%
1.
9%
2.
77%
3.
9%
4.
Mechanical potential energy
Non-mechanical potential energy
Mechanical kinetic energy
Non-mechanical kinetic energy
Which of the following best describes the motion
of the atoms in a cup of hot chocolate?
0%
1.
42%
2.
0%
58%
3.
4.
Mechanical potential energy
Non-mechanical potential energy
Mechanical kinetic energy
Non-mechanical kinetic energy
Which of the following best describes a
wound up clock spring?
68%
1.
23%
2.
5%
3.
5%
4.
Mechanical potential energy
Non-mechanical potential energy
Mechanical kinetic energy
Non-mechanical kinetic energy
Which of the following best describes a
clock spring unwinding?
4%
1.
4%
2.
92%
3.
0%
4.
Mechanical potential energy
Non-mechanical potential energy
Mechanical kinetic energy
Non-mechanical kinetic energy
Which of the following best describes a
skateboarder sitting at the top of a hill?
46%
1.
50%
2.
0%
3.
4%
4.
Mechanical potential energy
Non-mechanical potential energy
Mechanical kinetic energy
Non-mechanical kinetic energy
Which of the following best describes the energy within
the bonds between the atoms in a bowl of cereal?
0%
1.
82%
2.
9%
3.
9%
4.
Mechanical potential energy
Non-mechanical potential energy
Mechanical kinetic energy
Non-mechanical kinetic energy
Why does a dropped tennis ball not
return to its original position?
27%
1.
2.
14%
3.
36%
23%
4.
Energy is lost
Nonmechanical energy is converted to mechanical
energy
Mechanical energy is converted to nonmechanical
energy
There is not enough potential energy
A boulder has 600 J of PE. Ignoring
air resistance, approximately how
much KE does it have right before it
hits the ground?