1. Potential vs. Kinetic Energy
Friday, February 6th, 2015

2. Do Now Enter silently and complete quiz # 14, last word is tungsten
when you are finished copy down vocabulary
You can use a calculator for the worksheet
gravitational PE
PE=mgh (units=Joules J)
g=gravity 9.8m/s
KE=1/2mv2
(units=Joules J)
stored energy in a system
Energy of an
object in motion
at that time
m=mass (kg)
v=speed (m/s) (velocity)
m=mass (kg)
h=height (m)
Kinetic Energy
Potential Energy
An apple on a tree
Gasoline in a car
ball=0.5 kg
A falling apple
A moving car
mass=80 kg
speed=8 m/s
PE=
1 meter
KE=

3. Objectives
SWBAT identify a scenario that demonstrates the law of conservation of energy by calculating the potential and kinetic energy.
Essential Questions
What is the relationship between potential and kinetic energy? How is this related to the law of conservation of energy?

4. Demonstrating the law of conservation of energy
I have a marble with a mass of 10.2 grams
We need to convert that to __________
I have a 1 meter stick
We convert that to _____________
Speed of the marble when it hits the table is √(19.6m/s)
What is the potential energy?
What is the kinetic energy?

5. Law of conservation of energy (we are in a vacuum to ignore air resistance)
Potential Energy of a 0.1 kg marble 1 m off of the ground
PE=mgh
PE=(0.0102kg)(9.8m/s2)(1m)
PE= J
Kinetic Energy when it hits the ground
v2=2(h)(9.8m2/s2)
v2=19.6(1)m2/s2
KE=1/2mv2
KE=[(0.0102kg)√(19.6m/s)2]/2
KE= J
Joules=(kg)(m2/s2)
Some semi-complicated
math to find the speed of
the marble when it hits
the ground
More explanation
on how we calculate
speed at the ground

6. Answer the Essential Questions
What is the relationship between potential and kinetic energy? How is this related to the law of conservation of energy?
Answer in ONE complete sentence for EACH question
If an object is held at a specific height, the potential energy will be the same as the kinetic energy when the object hits the ground. This means that all of the energy transfers from potential energy to kinetic energy and no energy is created or destroyed.

7. Exit Ticket
A 20 kg rock is dropped off of the top of the AT&T building (188 m). The velocity when it hits the ground is √(3684.8) m/s2 ~ m/s2).
What is the potential energy of the rock at the top of the building? PE=mgh
What is the kinetic energy of the rock at the ground? KE=(1/2)mv2
Are they the same? Different? Why?