Tuesday, February 14th
Happy Valentines Day!
Bell Work
• Draw a Transverse Wave and
label its crest, trough, amplitude,
and wavelength.
Tuesday, February 14th
Happy Valentines Day!
Kinetic Energy & Potential Energy
Goals for Today:
• Content Objective: given an object’s mass and
velocity, and the equation for Kinetic Energy,
you will be able to calculate the object’s KE
using THE 4 STPES!
• Literacy Objective: You will be able to define
kinetic energy and give an example of an
object that has some.
Does the Ball have Energy?
• When I hold the baseball, does it have
energy?
• When I drop it, does it have energy when it is
falling?
• What about when it hits the ground?
• Where did that energy come from?
The Baseball had 2 Types of Energy
• Potential Energy – stored energy, due to
position (above the ground) or condition
• Kinetic Energy - energy a moving object has
because of its motion
• When did the ball have Potential Energy?
• When did it have Kinetic Energy?
Kinetic Energy
• All moving objects have Kinetic Energy
• A moving car, a thrown javelin, a rolling
bowling ball, a running horse, someone riding
a dirt bike
• We can calculate the amount of kinetic energy
a moving object has using the equation:
KE = ½ * mass * velocity2
KE = ½ m v2
KE = ½ * mass * velocity2
• Kinetic Energy depends on:
– MASS
– VELOCITY
• Kinetic Energy is measured in Joules
– “ J ” for short
I’ll use THE 4 STEPS to solve for KE:
KE = ½ m v2
• A person riding a dirt bike is traveling at 15 m/s.
The weight of the bike and the person total 140
kg. What is their Kinetic Energy (KE)?
• Step 1. What Information are we given?
• Step 2. What information do we need?
• Step 3. What equation will we use?
• Step 4. Insert Info and Solve.
Now let’s try Together
• A horse is walking around, grazing. He weighs
520 kg and is moving at 2 m/s. What is it’s
Kinetic Energy?
• Step 1. What Information are we given?
• Step 2. What information do we need?
• Step 3. What equation will we use?
• Step 4. Insert Info and Solve.
Try one in your Groups
• You are target shooting, using 9 mm bullets.
The bullets weigh 0.115 kg and travel at a
velocity of 340 m/s once they’re shot. What is
this moving bullet’s Kinetic Energy?
• Step 1. What Information are we given?
• Step 2. What information do we need?
• Step 3. What equation will we use?
• Step 4. Insert Info and Solve.
On Your Slip of Paper
• 1. Please define Kinetic Energy. Give an
example of an object that has Kinetic Energy.
• 2. Using THE 4 STEPS, find the Kinetic Energy
of a school bus with mass 10,000 kg if it is
traveling down Beavercreek Road at 20
meters/second?
• --When You Are Done: Flip Paper Over, Remain
Quiet, and Relax
A Couple Energy Jokes
• Why did the Gardner plant a light bulb?
• He hoped to grow a Power Plant!
• For this one, know that electricity is
measured in a unit called a “Watt”
• As Seen on a Sign off Hwy 213:
– You Can Trust Our Electricians, We Know
Watts Watt.
We Already Introduced Potential
Energy, but let’s refresh our brains:
• Potential Energy – stored energy, due to
position (above the ground) or condition
• I’ve found the man with the MOST Potential
Energy – a type of energy called Gravitational
Potential Energy
• http://www.youtube.com/watch?v=e335kbl9Y
Wc&feature=player_embedded
Gravitational Potential Energy
• Today we are going to be talking about a type
of Potential energy called Gravitational
Potential Energy
• Gravitational Potential Energy – stored energy
by objects due to their position above Earth’s
surface
Gravitational Potential Energy
• Anything that can fall has stored energy
• Amount of Potential Energy depends on:
– The object’s mass
– How high above the Earth’s surface it is (height)
• The equation for GPE
GPE= mass *gravity * height
GPE = mgh
Climber Man’s GPE
•
•
•
•
GPE = mass * gravity * height
Let’s Say he weighs 160lbs, which = 80 kg
Gravity is always 9.8 m/s/s
Climber man stood at 1,768 feet at the top.
1,768 ft = 540 meters
• GPE = mass * gravity * height
• GPE = (80kg)(9.8 m/s/s)(540m)
• GPE = 423,360 J
What does 423,360 J really mean?
• If Climber Man fell into a 10,000 gallon pool,
his 423,360 J would be able to instantly raise
the temperature of the 10,000 gallons by 1
degree C!
Comparing Object’s GPE
• Let’s compare one student sitting on a stool.
• To one student sitting on a text book.
• Let’s assume the students have about the
same mass
• Who has more Gravitational Potential Energy?
Another Comparison
• A hiker just summitted Mt. Hood, which
stands about 11,000 feet tall. He stands
proudly on the snowy mountain ground and
poses for a picture.
• A second hiker, starting her journey, pulls over
in Government Camp and stands on dry,
snow-less pavement planning her hike on her
map.
• Which of the two hikers has more
Gravitational Potential Energy?
Other Side of your Slip of Paper
• A can of Monster Energy drink is sitting on the
top shelf in your refrigerator. Two shelves
below is a can of Mountain Dew.
• Which of the two energy-filled drinks has the
most Gravitational Potential Energy.
• Why?