Download Chapter 9 Motion Notes

Chapter 9
Energy and Energy Resources
Kinetic and Potential Energy
9:1
Terms
• Energy- the ability to do work
– Unit: joules (J)
• Work- involves a transfer of energy and occurs
when a force causes an object to move in the
direction of the force ( work = force x distance)
– Unit: joules (J)
Kinetic Energy
• energy of motion
• All moving objects have kinetic energy
• Kinetic energy depends on speed and mass
K.E. = m v2
2
• K.E. = kinetic energy m = mass v = velocity
• faster objects — more kinetic energy
• objects with more mass — more kinetic energy
Try This
1. What is the kinetic energy of a turtle with a
mass of .9 kg moving at .05 m/s?
2. What is the kinetic energy of a 6,400 kg tractor
trailer traveling at 25m/s?
Potential Energy
• energy an object has because of its position or
shape.
• Example: stretching a rubber band changes its shape.
This gives it elastic potential energy.
• Gravitational potential energy- energy an object
has due to its position above the Earth's surface.
– Example: lifting up the rubber band gives it G.P.E.
– Depends on the height and the weight of an object
– G.P.E. = weight x height
Mechanical Energy
• the total energy of motion and position of an
object.
M.E. = P.E. + K.E
• M.E. = mechanical energy
• P.E. = potential energy
• K.E. = kinetic energy
• Mechanical Energy can be all potential energy, all kinetic energy or
part potential and part kinetic energy
Forms of Energy
9:1 continued
Thermal Energy
Thermal Energy- total energy of particles that make up an
object.
• Particles at higher temperatures have more thermal
energy(because they are moving faster) than the same
number and kind of particles at a lower temperature
• Increasing the number of particles you have in an object
increases the thermal energy
• Mostly kinetic energy
• Examples: stove, heater, Atlantic Ocean, curling iron,
furnaces, etc.
Chemical Energy
Chemical Energy- energy of a compound that
changes as its atoms are rearranged to form new
compounds
• Much potential energy stored in chemical bonds
• Potential energy is converted to kinetic energy
during the chemical reaction
• Examples: food, carbohydrates, gasoline,
kerosene, butane, firewood, etc.
Electrical Energy
Electrical Energy- energy of moving electrons
• Mostly kinetic energy
• Examples: TV, VCR, flashlight, computer,
calculator, & anything electrical or battery
operated
Sound Energy
Sound Energy- caused by vibrations of an object
• Potential energy is converted into kinetic energy
• Potential energy- example: stretching the string
of a guitar
• Kinetic energy- the string moving and vibrations
occurring in the air
• Examples: speakers, singing, musical
instruments, sonar, ultrasounds, taping on a
desk, etc.
Light Energy
Light Energy- produced by the vibrations of
electrically charged particles
• Mostly kinetic energy
• Electromagnetic radiation
• Examples: radio waves, visible light, radar,
microwaves, infrared radiation, UV rays, x-rays,
gamma rays, etc.
Nuclear Energy
Nuclear Energy- the energy associated with the changes in
the nucleus of an atom (the nuclei split or join together)
• Potential energy is converted into kinetic energy
• Potential Energy stored in the nucleus of an atom
• Kinetic Energy when the nucleus is split (fission) or joins
with other nuclei (fusion)
• Examples: nuclear fusion in stars and in the sun, nuclear
fission at a nuclear power plant, nuclear bombs, some
types of radiation therapy, radioactive decay,
Energy Conversions
9:2
Terms
Energy Conversion
– A change from one form of energy into another
Energy Efficiency
– A comparison with the amount of energy before a
conversion with the amount of useful energy after a
conversion
From Kinetic to Potential and Back
Conversions Involving Chemical Energy