Activity 5.3.4 Energy
Introduction
Energy is in everything. Energy provides change; it does things for us. It bakes
brownies in the oven and keeps ice frozen in the freezer. It plays our favorite songs
on our iPod and lights our homes. We use energy to do everything we do, from
making a jump shot to making our bodies grow to sending astronauts into space.
There are two types of energy, stored (potential) energy and working (kinetic)
energy. For example, the food you eat contains chemical energy, and your body
stores this energy until you release it when you work or play.
To scientists and technologists, conservation of energy is not saving energy. The
law of conservation of energy says that energy is neither created nor destroyed; it
simply changes from one form to another. When we use energy, it doesn’t
disappear. We change it from one form of energy into another. A car engine burns
gasoline, converting the chemical energy in gasoline into mechanical energy. Solar
cells change radiant energy into electrical energy. Energy changes form, but the
total amount of energy in the universe stays the same.
Chemical
Radiant
Motion
Chemical
Chemical
Motion
Electrical
Thermal
Project Lead The Way, Inc.
Copyright 2010
GTT – Unit 5 – Lesson 3 – Activity 5.3.4 – Energy – Page 1
Energy efficiency is the amount of useful energy you gain from a system. A perfectly
energy-efficient machine would change all of the energy put in the system into useful
work; an impossible dream. Converting one form of energy into another form always
involves a loss of usable energy. In fact, most energy transformations are not very
efficient. The human body is a good example. Your body is like a machine, and the
fuel for your machine is food. Food gives you the energy to move, breathe, and
think. But your body isn’t very efficient at converting food into useful work. Your body
is less than five percent efficient most of the time. The rest of the energy is lost as
heat. You can really feel that heat when you exercise!
In this activity you will experiment with potential and kinetic energy and calculate the
amount of work being done and the amount of each type of energy in the systems.
Equipment
 GTT notebook
 Pencil
Potential Energy/Work Lab
 Bricks or books
 ½ Cardboard tube or ruler with groove (to be used as a ramp)
 Metric balance scale or kitchen scale
 Ball bearings or marbles – 2 different mass values
 Plastic or Styrofoam cup cut in half
 Stop watch
 Meter stick or metric tape measure
 Masking or duct tape
Rollback Can
 Small clear plastic container that can be laid on its side and rolled with a hole
punched in its top and bottom (i.e., clear plastic soda bottle, peanut butter jar,
or mayonnaise jar) Note: Using a clear bottle or jar helps to demonstrate what
is happening inside.
 One thick rubber band about 3-4 inches long (8-10 cm)
 Two toothpicks or paper clips
 Several washers
 Twist tie
 String
 Hole punch tool or scissors
 Meter stick or metric tape measure
Procedure
In this activity your group will gather data and answer questions about each of the
activities that you create and observe. Be as accurate as possible when gathering
your data since you will use your data to complete calculations. Do not forget to
include units on all measurements.
Project Lead The Way, Inc.
Copyright 2010
GTT – Unit 5 – Lesson 3 – Activity 5.3.4 – Energy – Page 2
Answer the conclusion questions at the end of each activity and submit this lab to
your teacher for evaluation.
Potential Energy/Work Lab
1. Use the brick or books and cardboard tube or ruler to build a ramp. You need to
set this up in an area where you have plenty of room for your marbles or ball
bearings to roll. Place your half cup at the bottom of the ramp so that a marble
rolling down the ramp will enter the cup and push it a short distance.
Weigh each of your marbles/ball bearings and record the value in kg below. Add a
descriptor so you can identify each one. If your metric balance measures in grams;
1000g = 1 kg
Example: 650 g = .650 kg
150 g = .150 kg
75 g = .075 kg
2.
#1 Mass ________ Describe__________________________________________
#2 Mass ________ Describe__________________________________________
3. Use the marble or ball bearing with the smallest mass value. Release it from
halfway up each ramp three times. Use a metric tape measure to record the
distance the cup travels. Calculate the average distance the cup moved. Repeat,
but this time roll the marble or ball bearing from the top of the ramp three times
and calculate the average distance the cup travels. Repeat again, using the
sphere with the largest mass. The height is the perpendicular distance from the
table to where the sphere starts to roll.
Marble #
Height
Distance in cm that the
cup travels when marble
is released halfway up
ramp
Roll 1 ______________
Roll 2 ______________
Roll 3 ______________
Height
Distance in cm that the cup
travels when marble is
released at top of ramp
Roll 1 ______________
Roll 2 ______________
Roll 3 ______________
Avg. _______________
Avg. _______________
Roll 1 ______________
Roll 2 ______________
Roll 3 ______________
Roll 1 ______________
Roll 2 ______________
Roll 3 ______________
Avg. _______________
Avg. _______________
4. Describe the relationship between the distance the cup moves when the marble
is released at the top of the ramp compared to halfway up the ramp.
Project Lead The Way, Inc.
Copyright 2010
GTT – Unit 5 – Lesson 3 – Activity 5.3.4 – Energy – Page 3
5. Predict how far the cup will move if the marble is released ¾ of the way up the
ramp. Explain your answer.
6. Describe the relationship between the distance the cup moves when the sphere
(marble or ball bearing) has more mass.
7. Calculate the potential energy of the spheres using the formula:
Potential energy (J) = m(kg) x g(10 m/s2) x H(m)
The value of H is the perpendicular height from the table to where the sphere
starts to roll. Examples: 100 cm = 1 m 50 cm = .50 m
15 cm = .15 m
(mass)
x
(gravity)
x
(height)
= Potential Energy (J)
Marble #1 from
½-way up ramp
Marble #1 from
top of ramp
Marble #2 from
½-way up ramp
Marble #2 from
top of ramp
8. Using the same ramp set-up, measure and mark a distance 1 meter from the end
of your ramp with a piece of masking or duct tape. Use the stopwatch to time
how long it takes the marble to roll from the end of the ramp to the tape (do not
use the cup). Be ready to time – it’s going to go quickly.
Marble #
Marble #1
(smaller mass)
Marble #2
(larger mass)
Time when sphere is released
¼ way up ramp
Roll 1 ______________
Roll 2 ______________
Roll 3 ______________
Time when sphere is released
at top of ramp
Roll 1 ______________
Roll 2 ______________
Roll 3 ______________
Avg. _______________
Avg. _______________
Roll 1 ______________
Roll 2 ______________
Roll 3 ______________
Roll 1 ______________
Roll 2 ______________
Roll 3 ______________
Avg. _______________
Avg. _______________
Project Lead The Way, Inc.
Copyright 2010
GTT – Unit 5 – Lesson 3 – Activity 5.3.4 – Energy – Page 4
Conclusion
1. Describe the effect that the mass has on how quickly the sphere travels.
2. Describe the effect that the height from where you release the sphere has on the
time it takes to travel 1 m.
3. The formula for kinetic energy is:
Kinetic energy (J) = ½ x mass (kg) x velocity2 (m/s)
or
KE = ½ mv2

Which experiment in #8 has the highest kinetic energy? Why?

Which experiment in #8 has the lowest kinetic energy? Why?
Roll-back Toy – Elastic Potential Energy
1. Punch a hole through the lid and the bottom of
the container. Remove the container lid.
Thread a string through the bottom of the
container and pull it through the lidless top of
the container (make sure that string is left
hanging out the bottom end).
2. Tie the end of the string that you pulled
through the top to one end of the rubber band
(you will use the string as a lead to help thread
the rubber band through the container).
3. Use a twist tie to tie together several washers or another weighting device that
will fit through the opening of a soda bottle or the container being used. Connect
the washers to the middle of one section of the rubber band (do not tape the
strands of the rubber band together).
4. Put the end of the rubber band (the end not connected to the string) through the
container lid. Use a toothpick or paper clip to secure the band so that it does not
slip inside the container (put the toothpick through the end loop of the rubber
Project Lead The Way, Inc.
Copyright 2010
GTT – Unit 5 – Lesson 3 – Activity 5.3.4 – Energy – Page 5
band that remains outside the hole). Put the lid on the container (make sure that
string is still left hanging out the other end).
5. Carefully pull on the thread until the rubber band comes through the hole. Secure
the band with the second toothpick or paper clip. Fix both toothpicks with tape so
they will not shift when the rubber band is wound. Be sure to situate the weight in
the center of the container without touching the sides. Your roll-back toy is ready
to go!
6. Roll the toy and watch as the weight holds one strand of the rubber band
stationary while the free side twists around. Provide the can with potential energy
by turning it 10 revolutions. Release the can. Explain what happened.
7. Provide the can with the same amount of potential energy and measure the
distance the can rolls forward and backward. Record your measurements below
– don’t forget your units.
8. What do you think will happen if you turn the can 20 revolutions?
9. Test your prediction. Explain what your rollback can actually did.
10. How many revolutions do you think would be required to move your rollback can
10 meters? Explain how you got this answer.
11. Test your prediction. Did your can move 10 meters? Why or why not?
Project Lead The Way, Inc.
Copyright 2010
GTT – Unit 5 – Lesson 3 – Activity 5.3.4 – Energy – Page 6
Conclusion
1. How could you wind up the rubber band if you didn’t place the can on a table top
or floor?
2. What is the difference between elastic and gravitational potential energy?
3. When you push the can, you give it kinetic energy. When the rubber band winds
up inside the can, you are storing elastic potential energy in the stretched rubber
band.

When does the rollback can have the most kinetic energy?

What happens to the kinetic energy as the can rolls forward?

When does the rollback can have the most elastic potential energy?

What happens to the elastic potential energy as the can rolls backward?
Project Lead The Way, Inc.
Copyright 2010
GTT – Unit 5 – Lesson 3 – Activity 5.3.4 – Energy – Page 7