Download The Nature of Energy

The Nature of Energy
• An unbalanced force must be applied to an
object to change its motion.
• Work is the force over a distance.
• Energy is the ability to do work. Energy is
the ability to cause change.
Types of Energy
• There are 5 types of energy.
–
–
–
–
–
Heat energy
Chemical energy
Electrical energy
Solar energy
Nuclear energy
Kinetic Energy
• The energy of
• Example: run, walk, fall, or jump.
• 2 factors
• The size of the object (mass)
• Speed (faster = more kinetic energy)
Calculating Kinetic Energy
• Equation:
• Kinetic Energy = ½ mass x Velocity²
• The SI unit for energy is the Joule (jewel).
• Because velocity is squared in the equation
for kinetic energy, increasing the velocity of
an object can produce a large change in its
kinetic energy.
Heat Energy
• A form of Kinetic energy.
• Heat is caused by the random motion and
vibration of atoms and molecules in
substances.
• Temperature is how we measure the amount
of heat.
• Hotter the object, the faster the particles are
moving.
Potential energy
• The energy that an object is able to store
because of its position or condition.
• Gravity and size help items with potential
energy.
•
Potential energy is stored in the
•
swing where it starts and stops,
but converts to kinetic energy in-between.
Types of Potential Energy
• 1) Elastic Potential Energy
• Elastic Potential energy is energy stored by
something that can be stretched or
compressed, such as a rubber band or
spring.
Types of Potential Energy
• 2) Chemical Potential Energy
• Energy that is stored in chemical bonds.
Types of Potential Energy
• 3) Gravitational Potential Energy
(GPE) is energy stored by objects that
are above Earth’s surface.
The amount of gravitational potential energy
depends on 3 things:
A) mass
B) Acceleration due to gravity (9.8 m/s²)
C) height measured in meters
(GPE) Formula
• GPE = mass x 9.8 x height
• GPE is measured in Joules.
• Problem: a .06-kg tennis ball starts to fall
from a height of 2.9 meters. How much
gravitational potential energy does the ball
have at that height?
Solving the Problem
• Mass = .06 Acceleration = 9.8 Height =
2.9m
• (GPE) M x A x H
• .06 x 9.8 x 2.9 =
• (GPE) = 1.7 Joules
The Transformation of Energy
• Energy can change from one form to
another.
• PE
KE
• Chemical Energy
PE
Heat Energy
– Heat energy includes both exothermic and endothermic
reactions.
Electrical Energy
• Electricity is formed by the movement of
electrons.
• Electrons are negative.
• Electricity can produce heat, light, sound,
and magnetism. Electrical energy is
transformed into another form of energy.
Chemical Energy
• A form of potential energy
• The molecules store energy in their bonds
formed by their shared electrons.
• When the bonds break, they release energy
(kinetic) such as thermal energy.
Conversions Between Kinetic and
Potential Energy
• PE
KE
PE
• Mechanical Energy is the total amount of
potential and kinetic energy in a system.
• Equation = Mechanical energy =
– Potential energy + kinetic energy
– Mechanical energy is energy due to the position and the
motion of an object.
Energy Transformation
• Most objects are sitting with a maximum
potential energy or PE, but if the object
starts to move, then the PE changes into
Kinetic Energy. When the object has
stopped moving, then the KE transforms
back into the PE again.
• Example: An apple falling from an apple
tree.
The Law of Conservation of Energy
• The Law of Conservation of Energy states
that energy cannot be created or destroyed.
In a larger picture, this law means that the
total amount of energy in the universe
remains constant.
Where does energy go?
• Most energy is transformed into heat
Nuclear Energy
• When large nuclei split apart, they release free
neutrons and energy. (nuclear fission)
• Joining the nuclei of smaller atoms together can
also release stored nuclear energy. (Fusion)
• Example: The sun
Power Driven Machines
• Hydroelectric plant uses power from falling water
to turn machines that make electricty. The
Electricity is carried by wires to your home so
they may convert from electricity to heat or light.
• Combustion Engines (automobiles) convert
chemical energy (gas or fossil fuel) into heat
energy and then into mechanical energy
Longitudinal wave
Mechanical Waves
Sound waves
• Example: water or sound waves.
• The type of material that waves travel
through is called a medium. (gas, liquid, or
solid)
• Sounds travel faster in solids and liquids
because the particles are closer together.
Transverse wave
Electromagnetic Waves
• Electromagnetic waves, (radio, light), do
not require a medium to pass through. They
can travel through a vacuum (space), and do
not require particles of matter to carry their
energy.
Electromagnetic Spectrum
• Radio, microwave, infrared, visible light,
ultraviolet, X-rays, and gamma rays make up the
electromagnetic spectrum.
• All these waves travel at the same speed, but their
frequencies and wavelengths differ.
• Radio waves have the lowest frequency/ longest
wavelengths, whereas gamma rays have the
highest frequencies and the shortest wavelengths.