Transcript Energy - Mandan Public School District

Chapter 4
The nature of energy
 Energy: The ability to
do work or cause
change
 All energy involves
either motion or
position
 Where are we using
energy right now?
What are some types of energy?
 Thermal energy : The total
 Electrical energy: the
kinetic energy of particles
that make up an object
 Chemical energy: The
energy of a compound
changes as the atoms are
rearranged to form new
compounds.
energy of moving electrons
 Sound energy: The energy
of vibration
 Light energy: The energy of
vibration of electrically
charged particles
 Nuclear energy: the energy
associated with changes in
the nucleus of an atom
Mechanical NRG
 Mechanical energy is
the total amount of
potential and kinetic
energy in a system
Kinetic energy
 Kinetic energy is energy in the form of motion.
Potential energy is stored energy because of
position or shape
Energy transfer
How to calculate kinetic energy:
 Kinetic energy = ½ (mass x
 What is the kinetic energy
velocity 2) or

KE = ½ (mv2)

 Labeled as Joules
 Joule is expressed in
m or
 1 Joule= 1 kg * (m/s)2
Nx



of a 45 kg object moving at
13 m/sec?
mass = 45 kg
velocity =
13 m/sec
KE = ½ (mv2)
So…
KE = 1/2 (45
kg)(13 m/sec)2
Solving the equation gives
a kinetic energy value of
3802.5 J
Calculate
 Determine the kinetic
 If the roller coaster car in
energy of a 1000-kg roller
coaster car that is moving
with a speed of 20.0 m/s.
 KE = (0.5) * (1000 kg) * (20
m/s)2
 KE = 200 000 Joules
the above problem were
moving with twice the
speed, then what would be
its new kinetic energy?
 KE = 0.5*1000 kg*(40
m/s)2
 KE = 800 000 Joules
 As your speed doubles your
kinetic energy quadruples.
Gravitational Potential Energy
 Grav. Potential energy =
 A 37 N object is lifted to
weight x height
 Or…..
 PE = w x h
 Elastic Potential energy:
energy stored by
compressing or
stretching something
a height of 3
meters. What is the
potential energy of this
object?
 weight = 37 N height = 3
meters
 Solving the problem
gives a potential energy
value of 111 J.