Transcript energy - Images

ENERGY
 You
are walking from your
math class to your science
class. You are carrying
books using a force of 20
N. You walk 45 m down
the hall, climb 15 m up the
stairs, and then walk
another 30 m to your
science class. What is the
total work performed on
your books?
ENERGY
 The
ability to do work
or cause change
Work: when a force
is used to move an
object a distance
ENERGY
2
types of energy
Kinetic
Potential
Whether it is kinetic or
potential depends on
whether the object is
moving or not
Potential Energy
Energy
that is
stored and held in
readiness
Has the potential
to do work
Potential Energy
 Elastic
Potential Energy
 PE associated with
objects that can be
stretched or
compressed
 Example: rubber band
Potential Energy
 Gravitational
Potential
Energy
 PE to an object when you
lift it
 Potential energy that
depends on height
 The GPE an object has is
equal to the work done to
lift it.
Work
= Force x Distance
Potential Energy
 Calculating
gravitational
potential energy
 GPE
= weight x height
Newton-meter = (newtons) x (meters)
(joules)
= mass x 9.8m/s2 x
height
 GPE
 Gravitational
9.8m/s2.
acceleration is
Potential Energy
A hiker climbs 40 meters up a
hill. He weighs 680 newtons.
How much gravitational
potential energy does he have
at the top of the hill.
 GPE = weight x height
 GPE = 680n x 40m
 GPE = 27, 200 J or newtonmeters

Kinetic Energy
 Energy
of motion
 Depends on both mass
and velocity
 Velocity:
speed in a
given direction
Kinetic Energy
 Calculating
kinetic
energy
= mass x velocity2
2
*Changing velocity will
have a greater effect on
KE than changing its
mass.
 KE
Kinetic Energy

Find the kinetic energy for the
following:
A
10kg wagon moving at 5m/s
 A 10kg wagon moving at 10m/s
 A 20 kg wagon moving at 5m/s
 Which
has the greatest
kinetic energy?
Different Forms of
Kinetic & Potential
Energy
 Mechanical
 Thermal
 Chemical
 Electrical
 Electromagnetic
 Nuclear
Mechanical Energy
 Energy
associated with
motion or position of an
object
 Can occur as kinetic or
potential
 Example: riding a bus,
hearing a sound, leaping
frog
Thermal Energy
 The
total energy of the
particles in a substance
 All matter is made up of
atoms & molecules.
 The
particles have both
potential & kinetic energy due
to their arrangement and
motion
Chemical Energy
 Potential
energy stored in
chemical bonds that hold
chemical compounds
together
 Chemical compounds
store chemical energy
 Chocolate,
wood, wax
 Stored in food, cells in
body
Electrical Energy
 Moving
electrical
charges produce
electricity; the energy
they carry is electrical
energy
 Batteries, power lines
Electromagnetic
Energy
 Travels
in waves
 Have some electrical
properties
 May have magnetic
properties
 Examples: light, uv
radiation, microwaves,
infrared radiation
Nuclear Energy
 Type
of potential energy
 Stored in the nucleus of
an atom and is released
during nuclear reactions
 Nuclear
fission
 Nuclear fusion