15.1 Energy and Its Forms
Energy and Work
•Energy is the ability to do ____.
–Work is a transfer of __________
• Energy is known by the changes
it causes.
• Work is done when a force
moves an object through a
distance.
• Energy is transferred by a force
moving an object through a
distance.
• Both work and energy are
typically measured in joules (J).
15.1 Energy and Its Forms
Energy and Work
Energy has different forms.
A. The sun gives off energy in the form of heat and
light.
B. Plants convert sunlight into food.
C. People convert food energy into muscle
movement.
15.1 Energy and Its Forms
Kinetic Energy
• The energy of motion is called __________energy.
• The kinetic energy of any moving object depends
upon the object’s mass and ____________.
– Doubling mass in the formula doubles the kinetic energy.
– Doubling speed quadruples the kinetic energy.
15.1 Energy and Its Forms
Kinetic Energy
Calculating Kinetic Energy
A 0.10-kilogram bird is flying at a constant speed
of 8.0 m/s. What is the bird’s kinetic energy?
15.1 Energy and Its Forms
Kinetic Energy
1. A 70.0-kilogram man is walking at a speed of 2.0
m/s. What is his kinetic energy?
Answer:
15.1 Energy and Its Forms
Kinetic Energy
2. A 1400-kilogram car is moving at a speed of
25 m/s. How much kinetic energy does the car
have?
Answer:
15.1 Energy and Its Forms
Potential Energy
Potential energy: energy that is stored as a result of
position or ___________
Gravitational Potential Energy
•An object’s gravitational potential energy depends
on mass,______, and the acceleration due to gravity.
–This type of potential energy increases when an
object is raised to a higher level.
–Gravitational potential energy’s unit is joules.
15.1 Energy and Its Forms
Potential Energy
This diver has gravitational
potential energy as she stands
at the end of a diving board.
She gained the potential
energy by doing work—by
climbing up the steps to the
diving board.
15.1 Energy and Its Forms
Potential Energy
What is the potential energy relative to the water
surface of a diver at the top of a 10.0-meter-high
diving platform. Suppose she has a mass of 50.0
kilograms.
15.1 Energy and Its Forms
Potential Energy
Elastic Potential Energy
•The potential energy of an object that is stretched or
compressed is ________________potential energy.
–Something that is elastic springs back to its
original shape after it is stretched or compressed.
15.1 Energy and Its Forms
Potential Energy
When this musician pulls the string of
her cello to one side, the string is
stretched and gains potential energy.
The musician adds energy to the
cello string by plucking it.
• The energy stored in the stretched
string is potential energy.
• The stored energy is converted into
kinetic energy when the string is
released and it vibrates.
15.1 Energy and Its Forms
Forms of Energy
Each form of energy can be converted into other
forms of energy.
Mechanical Energy
•The energy associated with the motion and position
of ______________________is mechanical energy.
–Mechanical energy is the sum of an object’s
potential energy and kinetic energy.
–Mechanical energy is not limited to machines.
–Examples: speeding trains, bouncing balls,
running athletes, etc.
15.1 Energy and Its Forms
Thermal Energy
•The total potential and kinetic
energy of all the _____________
particles in an object make up its
thermal energy.
– When an object’s atoms
move faster, its thermal energy
increases, and the object
becomes warmer.
–This molten metal is
extremely hot. It contains a
great deal of thermal energy.
15.1 Energy and Its Forms
Chemical Energy
•The energy stored in chemical ____________.
– When bonds are broken, the released energy
can do _____________.
– All chemical compounds, including fuels such as
coal and gasoline, store energy.
–Chemical energy of burning wood produces
thermal energy for heating marshmallows.
15.1 Energy and Its Forms
Electrical Energy
•The energy associated with
electric ______________.
–Batteries and lightening are
examples of electrical energy.
Electromagnetic Energy
•The energy that travels through
space in the form of ___________.
–Visible light and X-rays are
examples of electromagnetic
energy.
15.1 Energy and Its Forms
Nuclear Energy
The nucleus of an atom is held together by strong
and weak nuclear forces, which can store an
enormous amount of potential energy.
• The energy stored in atomic nuclei is known as
nuclear energy.
• Nuclear __________releases energy by splitting
nuclei apart.
• Nuclear___________releases energy when less
massive nuclei combine to form a more massive
nucleus.