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Energy: The Ability to Do Work
• ENERGY is anything that has the ability to move a sample of matter against a force.
• ENERGY can come in many different forms: light, sound, electrical, chemical, heat, nuclear, and mechanical.
energyfriction
Energy: The Ability to Do Work
• All energy can be in one of two states:
KINETIC OR POTENTIAL.
• Kinetic energy (KE) is the energy of the motion of the sample of matter.
• When a sample of matter is moving, it has kinetic energy.
Energy: The Ability to Do Work
• Potential energy (PE) is the energy due to the position of the sample of matter.
• Potential energy is inactive or stored energy.
• Kinetic energy is active or released energy.
Energy: The Ability to Do Work
• Potential energy can be converted into kinetic energy.
Energy: The Ability to Do Work
• Kinetic energy can be converted into potential energy.
Energy: The Ability to Do Work
• The pendulum at the Parthenon in Paris shows the relationship between KE and PE.
Energy: The Ability to Do Work
the wire
Theweight
Pendulum pulledback in order tobegin motion.
Maximum PE.
Pendulum at bottom of swing.Maximum KE.
Pendulum at top of back swing.
Maximum PE.
Lowest KEHighest PE
Lowest KEHighest PE
Highest KELowest PE
Energy: The Ability to Do Work
• Skateboarders also demonstrate the conversion of kinetic energy to potential energy and back to kinetic energy.
Energy: The Ability to Do Work
Highest KELowest PE
Lowest KEHighest PE
Lowest KEHighest PE
Medium KEMedium PE
Medium KEMedium PE
Energy: The Ability to Do Work
• The kinetic energy of an object is determined by its mass and its speed.1) The faster an object moves, the
greater its kinetic energy will be.
2) The more massive an object is, the greater its kinetic energy will be.
A speeding bullet can have the same KE as a creeping truck .
Energy: The Ability to Do Work
• The potential energy of an object due to gravity is determined by its mass and its height off the ground.1) The higher an object is off the ground,
the greater its potential energy will be.
2) The more massive an object is, the greater its potential energy will be.
A truck and a penny can have the same PE.
Energy: The Ability to Do Work
• The potential energy of an object due to a spring is determined by the distance the spring is stretched or compressed and the spring’s force constant.1) The more the spring is stretched or compressed, the
greater its potential energy will be.2) The greater the spring’s force constant is, the its
potential energy will be.
A bullet in a spring gun can have the same PE as a person on a pogo stick .
Energy: The Ability to Do Work
• A change in temperature alters the average speed of the particles in a sample of matter, thus a change in temperature causes a change in kinetic energy.
vibratingslowly
low temperature solid
vibratingquickly
high temperaturesolid
Energy: The Ability to Do Work
• A change in phase alters the positions of the particles in a sample of matter, thus a change in phase causes a change in potential energy.
ordered, fixedpositions
solid at 80oC liquid at 80oC
disordered, changing positions
Energy: The Ability to Do Work
• According to the Law of Conservation of Energy, energy can neither be created nor destroyed but can change from one form to another without changing the overall amount of energy present. Thus the total energy of a system must remain constant. There is a conservation of energy!
Energy: The Ability to Do Workba
ttery
chemical energy
electrical energy
light energy & heat
