Download Chapter 2, Section 8

Chapter 2, Section 8
Potential and Kinetic Energy:
Energy in the Pole Vault
November 1, 2010
HW: 2.8 PTG #1, 2, 3, 6, 7, 8, 13, Due Friday
• Learning Objectives:
 Describe kinetic, gravitational
potential, and elastic energy
and the variables that
influence them
– Explain conservation of
energy
• Do Now:
– Write LO and SC in
notebook
– WDYS/WDYT
• pg 220
• Success Criteria:
– Apply equations for kinetic energy,
gravitational potential energy, and
elastic energy
– Recognize that restoring forces are
active when objects are deformed
– Apply the equation for the force
necessary to compress or stretch a
string
– Conduct simulations of
transformations of energy involved in
the pole vault.
• Agenda:
– Do Now
– LO/SC
Investigate #1-9
• Worksheet
2.8 Physics Talk
• What is happening
to speed at each
position?
3
2
4
1
1. Force gives the
ball an upward
speed
2. Speed decreases
as the ball is acted
upon by gravity
3. Vertical position is
maximum, but
vertical speed is 0
4. Ball increases in
speed as it is
acted upon by
gravity
2.8 Physics Talk
• What changed in
terms of energy?
• Total energy is
always the same, it
is just transformed
from one form to
another
2.8 Physics Talk
• What is Kinetic
Energy (KE)
• Energy associated
with motion
• What is
Gravitational
Potential Energy?
• The energy an
object possesses
because of its
vertical position
from Earth
2.8 Physics Talk
• What is potential
energy?
• Energy associated
with position
• What is the Law of
Conservation of
Energy?
• Energy cannot be
created or
destroyed! It can be
transformed from
one form to another
but the total energy
remains constant!
2.8 Physics Talk
• What changed in
terms of energy?
3
2
4
1
1. Ball has only
kinetic energy
2. Kinetic energy
decreases,
Gravitational
Potential Energy
increases
3. Kinetic Energy=0,
Max GPE
4. GPE decreases,
Kinetic Energy
increases
2.8 Physics Talk
• What energy is
needed to get the
ball moving? To get
it to stop?
• WORK!
• Work is the force
applied over a
distance
• Causes the change
in forms of energy
• What is the
equation for Work?
• Work=Force x Distance
• W=Fd
W
F
d
Think about launching the penny…
• Work was done on the ruler to add energy to
the system
• After bending the ruler it had Elastic Potential
Energy
• When you released the ruler it applied a force
over a distance to the penny (work)
• The penny now has Kinetic Energy
• As it travelled up, the KE became GPE
• At the peak, the penny had no KE and all GPE
• As the coin fell GPE became KE
• Sum of the GPE and KE was always the same
(conservation of energy)
Pole Vaulting!!!
• http://www.youtube.com/watch?v=kJu
citWzywM&feature=fvw
• Food energy provides muscular
energy to run which is KE
• Vaulter’s KE is converted to Elastic PE
in the pole
• As the pole unbends, EPE is
transferred to the vaulter as GPE
• As vaulter falls GPE is transferred to
KE
• Total energy remains the same!
Equations!!!
• Work
• W=Fd
F=force (N)
d=distance (m)
W=work (Joules J)
• Elastic (spring)PE
• EPE=1/2kx2
K=spring constant
(N/m)
x=amount of bend in
meters
EPE=Joules (J)
Equations!!!
• Gravitational
Potential Energy
• GPE=mgh
• Kinetic Energy
• KE=1/2mv2
GPE=Joules (J)
m=mass (kg)
g=gravity (m/s2)
h-=height (m)
KE=Joules (J)
m=mass (kg)
v=speed (m/s)
Practice Problems
•
•
•
•
•
Pg. 226-227
#1-Whole group
#2-Whole Group
#3-Small Group
#4-Individually
Vocab Activity
Book Definition
Definition in your words
2.8 Vocab Boxes.docx
Example or Equation
Picture/Drawing
Practice Problems
• Work and Energy Practice
Problems.pdf
Relay
• Energy Relay.pdf
• Work and Energy Relay.pdf