Energy
Lesson #3: Kinetic and Potential Energy
Time Frame: 60 minutes
Please write the vocabulary on the board before each lesson.
Vocabulary
Kinetic Energy - energy that an object has because of its motion
Potential Energy - stored energy; energy that an object has because of its position
Learning Standards:
Science
Energy
1) Use evidence to construct an explanation relating the speed of an object to the
energy of that object.
Science and Engineering Practices
1) Use evidence (e.g., measurements, observations, patterns) to construct an
explanation.
2) Make observations to produce data to serve as the basis for evidence for an
explanation of a phenomenon or test a design solution.
Engineering
Science and Engineering Practices
1) Plan and conduct an investigation collaboratively to produce data to serve as the
basis for evidence, using fair tests in which variables are controlled and the
number of trials considered.
Student will be able to:
1) Understand the difference between kinetic and potential energy and the relationship
between these two classes of energy.
2) Gain an understanding of the Law of Conservation of Energy.
3) Identify independent and dependent variables in an experiment.
Resources and Materials:
Item
Science Journals
iPads
Pendulum
Aluminum cans
Measuring tape
1 m wooden ramps
Ramp Racers Student Activity Sheet
Ramp Racers Student Record Sheet
Amount
1 (in bin)
5 (in bin)
5 (in bin)
5 (in classroom near bins)
25 (in bin)
25 (in bin)
Focus Activity: Demonstrate the swinging of a pendulum by lifting up a ball on a string
and allowing it to fall. Have students observe the motion and record their observations
in the science journals. Where is the ball moving the fastest?
Introduction: Write kinetic energy and potential energy on the board. Tell students that
today they will be learning about two different types of energy: kinetic energy and
potential energy. Energy is present wherever there are moving objects. Think of a car
speeding down the highway or a bird flapping its wings. Both require energy. The type
of energy that is at work when things move is called kinetic energy. But that energy
isn’t lost when the object stops moving. Think of the Law of Conservation of Energy -energy can neither be created nor destroyed. Therefore, it must be converted into
another type of energy. This type of energy is stored energy, or potential energy.
Potential energy is energy that is stored in an object due to its position. It is the energy
that an object has that gives it the potential to cause movement. The type of potential
energy we observed with the pendulum is called gravitational potential energy.
Use the pendulum from the following website as a model to explain kinetic and potential
energy: http://www.physicsclassroom.com/mmedia/energy/pe.cfm
When the ball is moving, it has kinetic energy. It has the most kinetic energy when it is
moving the fastest, when the ball is at the lowest point of the pendulum. This kinetic
energy, however, is not lost when it moves higher and decreases in speed. Kinetic
energy is converted into potential energy. An object that has a higher relative position
to the ground will have more potential energy, because it works against the force of
gravity. Gravity is constantly at work. Think of the expression “What goes up must
come down”. An object that is up in the air has potential energy due to its position.
When it falls, it has kinetic energy.
Activity:
1) Tell students that they will be experimenting with kinetic and potential energy to
see how quickly or slowly an object moves when starting from different positions
(heights). They will be rolling a can down a ramp and timing how quickly it
travels from the top to the bottom of the ramp.
2) Write independent variable and dependent variable on the board. Tell
students that they will be working with two types of variables in this experiment.
Ask students to recall that a variable is something that changes between trials.
An independent variable is the variable in an experiment that we directly
manipulate or change. A dependent variable is the change in the outcome that
occurs as a result of the independent variable. A good way to remember the
difference is that the dependent variable depends on the independent variable to
cause a change in the experiment. Identify the height of the ramp as the
independent variable in the experiment and the time it takes for the can to roll
down the ramp as the dependent variable.
3) Split the students into groups of 4 or 5. Have each group collect their materials
and take all materials into the hallway (or anywhere with a large, open space and
an even surface).
4) Find any surface to prop up one end of the ramp, and set the other end of the
ramp on the floor. Have students measure the length of the ramp using the
measuring tapes. This is the distance that the can will roll. It should always be 1
m. Explain to students that this is a constant in the experimental design. A
constant is something that remains the same in each trial.
5) Have students measure the height from the top of the ramp to the floor, and
record that value in the height column of the data chart on the worksheet
attached to the experiment. The distance that the aluminum can will travel on the
ramp should always be 1 m, because this is the length of the ramp.
6) Have students place their aluminum can at the top of the ramp and set their
stopwatches to zero. Students should use the timer app on the iPads. One
student should let the can go, and another student should immediately start the
stopwatch and time how long it takes for the can to roll down the ramp. Stop the
stopwatch when the can rolls onto the floor. Students should record the times in
their experiment record sheet.
7) Have students repeat the procedure for a total of three trials at the same height.
This is to ensure accurate measurement of times.
8) Then students should repeat the procedure for three more heights. Make sure
students record all of the heights and times they observe. You may
predetermine heights or allow students to choose their own heights, but students
should aim to have a broad range of heights from which to draw data.
9) When students have finished collecting their data, have them calculate speed to
create a graph. Students can use the calculator app on the iPads if necessary.
First, they should calculate the average time for each trial by adding the times
together and dividing by three. Then, they can calculate speed using the
following equation:
speed (m/s) = distance traveled (m) / time taken (s)
= 1m / time taken
Remember to keep the units in m/s when recording the speed on the worksheet.
10) Using the MetaCalculator graphing app on the iPads, students will graph their
results with the height of the ramp on the x-axis and the speed of the rolling can
on the y-axis. Ask students to transcribe the graph they create on the iPads to
the graph provided on the worksheet, and then describe any relationship they
see between the height of the ramp and the average speed of the rolling can.
Closure: As a class, discuss the relationship between the height of the ramp and the
average speed of the can. Remind students of the definition of energy from the
previous lesson: The faster a given object is moving, the more energy it possess.
Thus, the cans that roll with greater average speed have more energy. Since students
are not pushing the can down the ramp, ask students to think about where the energy of
the can comes from. In this activity, students have been experimenting with
gravitational potential energy. Gravitational potential energy depends on an object’s
distance from the ground and an object’s weight. The further away an object is from the
ground, the more gravitational potential energy the object has. Also, the heavier an
object is, the more energy it takes to lift that object to the same distance from the
ground, so the more gravitational potential energy the object has. When the can rolls
along the ramp, that gravitational potential energy is transformed into kinetic energy. By
the Law of Conservation of Energy, the more gravitational potential energy an object
has (the higher off the ground it is positioned), the more kinetic energy the object will
have after all the potential energy transforms into kinetic energy. Thus, cans with more
kinetic energy roll at greater speeds.
Play this video if time permits:
http://www.watchknowlearn.org/Video.aspx?VideoID=29751
Assessment: experiment sheet, participation, science notebooks
Name:_______________________________________
Date:________________
Ramp Racers!
Student Activity Sheet
Materials
1-meter ramp
stopwatch
can
pencil
books
ruler
What is the independent variable in this experiment?
What is the dependent variable?
Experimental Procedure:
1. Find any surface to prop up one end of the ramp, and set the other end of the ramp on
the floor. Measure the length of the ramp using your ruler. This is the distance that the
can will roll. It should always be 1 m. This is a constant in the experimental design. A
constant is something that remains the same in each trial.
2. Measure the height from the top of the ramp to the floor, and record that value in the
height column of the data chart on your student record sheet.
3. Place your aluminum can behind the line and set your stopwatch to zero. One student
should let the can go, and another student should immediately start the stopwatch and
time how long it takes for the can to roll down the ramp.
4. Stop the stopwatch when the can reaches the end of the ramp and rolls onto the floor.
Record the time in your experiment record sheet.
5. Repeat steps 2-4 of the procedure for a total of three trials at the same height. This is to
ensure precise measurement of times.
6. Repeat the procedure for three more heights. Make sure to record all of the heights and
all of the times that you observe.
Of the heights that you observed, which height caused the can to roll the most quickly? Why do
you think this would happen, in terms of energy?
Name:_____________________________________
Date:______________
Ramp Racers!
Student Record Sheet
Record your data in the chart below. Do three trials for each of the four heights. Be sure to use
a mix of heights in your experiment to test the effects of potential energy on speed.
To calculate average time for a given height, add your time for trial 1, trial 2, and trial 3, and
divide that number by 3, because there are three trials.
(T1+T2+T3)÷3= avg. time
Example: (3.0 seconds+ 3.4 seconds+2.9 seconds) ÷ 3 = 3.1 seconds
Height (cm)
Trial 1 Time
(s)
Trial 2 Time
(s)
Trial 3 Time
(s)
Average Time (s)
Calculate Speed!
Speed is a relationship between distance and time that measures how fast an object is moving.
When scientists calculate speed, they use the following equation:
distance traveled (m) / average time(s) = speed (m/s)
Remember that in this experiment, the distance traveled by the can does not change between
trials, because the length of the ramp is a constant. The can always travels a distance of 1
meter. Therefore, the equation you can use to calculate the speed of the can is:
1m / average time (s) = speed (m/s)
Trial 1 height:
Distance Traveled (m)
Average Time (s)
Speed (m/s)
Average Time (s)
Speed (m/s)
Average Time (s)
Speed (m/s)
Average Time (s)
Speed (m/s)
Trial 2 height:
Distance Traveled (m)
Trial 3 height:
Distance Traveled (m)
Trial 4 height:
Distance Traveled (m)