Download Kinetic and Potential Energy Answers

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NAME: _____________________________
ENERGY: KINETIC VS. POTENTIAL
Have you ever thought about.....why you are able to get out of bed in the morning and come to school?
Why the alarm clock sounds in the morning? How the toaster toasts bread? How your car runs? How you
run? Why your nose runs? How your computer runs? How everything runs? NO, you say? WHY
NOT?????? Do you not have enough energy? Funny, I said energy, because that is the answer to all of the
questions from above. Everything runs because of energy. In other words, energy is the stuff that makes
stuff do stuff!!!!!! Or in proper scientific talk: the ability to do work or cause change. In this
investigation, you will examine and analyze objects at rest and in motion in order to describe the
relationships that exist between the two types of stuff that make stuff do stuff (energy).
Objective
When you have completed this investigation, you should be able to analyze the movement of a pendulum in
order to describe the relationship between potential energy and kinetic energy in moving objects.
Materials
pendulum
Activity 1:
1. Observe the pendulum that your teacher has set up in front of the class.
2. Label the parts of the pendulum.
Fixed point
String, bar, or rod
Pendulum bob
3. Name the two types of energy displayed by the pendulum.
Kinetic energy
Potential energy
4. Observe the diagram in Figure 1.
C.
A.
B.
Figure 1
5. Circle which position(s) you believe have the greatest potential energy.
6. Place a box around the position(s) you believe have the greatest kinetic energy.
7. Read the selection below.
There are two basic types of energy, kinetic and potential. The word kinetic comes
from the Greek word kinetos which means "moving.” Therefore, kinetic energy (K.E.) is
simply described as energy of motion. If an object is moving, it has kinetic energy. Two
factors that affect the amount of kinetic energy an object has are mass and velocity
(speed). The other basic type of energy is potential energy (P.E.). Potential energy is the
opposite of kinetic energy. If kinetic energy is energy of motion, potential energy is energy
that exists even when an object is at rest. It can be simply described as stored energy or
energy that has the potential to do work. Potential energy can be the result of an object's
position, shape, or chemical make-up. Kinetic energy is the result of potential energy being
converted to action. A specific type of potential energy that describes energy of position
is known as gravitational potential energy (G.P.E.). Potential energy can be stored in any
object just because it occupies a higher position. The higher an object is the more G.P.E it
has. The kinetic energy resulting from the conversion of gravitational potential energy to an
object's movement is readily visible. Furthermore, a simple relationship exists. A falling
object has its greatest amount of kinetic energy when it is traveling its fastest.
8. Use the information in the reading selection to evaluate your predictions from tasks 4 and 5.
My prediction was…_________ right. I thought that
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The correct answer was….___________________
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Activity 2
9. Explore the following web page: http://www.walter-fendt.de/ph14e/pendulum.htm Be sure to select the
energy applet from the right hand side.
10. Describe the energy conversion that takes place in a pendulum.
As the pendulum falls, the potential energy turns into kinetic energy,
because it gains velocity and loses height. As the pendulum rises, the
kinetic energy turns into potential energy, because it gains height and
loses velocity.
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11. Look at the pendulum below, and label the places where it has the maximum and minimum potential
energy and kinetic energy.
max pot.
min kin.
C.
A.
max pot.
min kin.
B.
max kin.
min pot.
Activity 3:
12. Observe the movement of the pendulum in the teacher demonstration.
13. Describe the energy conversions of the pendulum from the time the pendulum starts to the point
when the pendulum stops.
When the pendulum starts, it has all potential energy.
As it falls, the potential energy is transformed into
kinetic energy. At the bottom, the energy is all kinetic.
As the pendulum rose the kinetic energy is transformed
back into potential energy. When the pendulum stops,
all of the energy is again potential energy.
14. What do you think causes the pendulum to eventually stop?
The pendulum eventually stops due to friction from the
air and at the point where the string is connected.
Law of Conservation of Energy
E.C.
Energy may not be created nor destroyed. It may only
be transformed from one form to another.
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Analysis (The Great Ball Drop)
1. Observe the diagram and caption.
Stanley Stick wants to roll his ball down a cliff
to show energy in action. He said,
 "The ball has the most energy just
before it hits the ground because it is
going fastest there!”
 “It has no energy at the top, because it is
not moving!!!”
2. Label the points of maximum and minimum potential energy and kinetic energy on the diagram.
3. Explain the error(s) in Stanley's thinking using information from today's investigation. Be sure to
mention points of maximum and minimum potential and kinetic energy. Address BOTH of Stanley’s
claims.
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4. Not all of the potential energy that exists at the top is directly converted to the kinetic energy of the
rolling ball. Determine what happens to this "lost" energy. (HINT: Think about friction and the law
of conservation of energy).
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