Red Rover – FLOW Teacher Guide
Grade Levels: 5th grade – 12th grade
Learning Goals:
1. Energy can be thought of in terms of transfer and storage.
2. Work is a mechanism for energy transfer.
3. Define and show comprehension of Mechanical Advantage.
4. Manipulate then discuss how a 3rd class lever differs from other classes.
Students will be exposed to the following vocabulary: fulcrum, lever, input (i.e., effort) force, output (i.e.,
resistance or load) force, load, input displacement, output displacement, product, ratio, equivalence.
Duration: Two 50 minute class sessions for each student to experience each role.
Prerequisite: Try to go to SMALLabLearning.com and play Traffic Jack scenario to understand first class levers.
How is this Embodied and Collaborative? It is embodied because the driver uses well-mapped, kinesthetically
congruent gestures to control the Rover-like vehicle. The second student, the Crusher, uses his/her arm length
to map to the location on the levers where pressure will be applied. It is collaborative because the two
students must work together to first capture the rock, then decide where the pressure should be applied
according the crack or crush mission.
Section
Action
Introduction Difference between work and
“Welcome to energy
the Red
Rover game.
Here we will
explore a
different
class of
lever.”
Teacher
Before playing the game we should revisit the concept of
energy because it is often confused with the concepts of
force and power and even speed.
Energy is “the ability to cause a change.”
One reason to use this more general definition is that the
term Work is one that is often misunderstood as well.
There are two things that can be done with energy—it can
be stored and/or it can be transferred. The transfer of
energy by means of Work happens by exerting a Force
across some Distance. The product of the input force and
the distance travelled is the work done on the object.
We use simple machines to help make work more efficient.
What are some simple machines you know?
Prior
knowledge
activation
Three classes of levers
SMALLab Learning, LLC
The lever is a simple machine.
There are three classes of lever. The most familiar is the first
http://smallablearning.com
1
class lever, where the fulcrum is situated between the input
and output forces. What are some examples of this?
(a teeter totter or a car tire jack)
A second class lever has the output force between the input
force and the fulcrum.
(examples, nutcracker or wheelbarrow)
A third class lever has the input force between the fulcrum
and output force.
(examples, tweezers, a fishing pole, the human arm (elbow)
1st class: input-fulcrum-output
2nd class: input-output-fulcrum
3rd class: output-input-fulcrum
Symbolic
section
The equations
The equation:
(W = F x d)
Distance is measured from the fulcrum to the input or
output force.
Work, like energy is a scalar quantity. This means that it is
simply a directionless magnitude.
Students need to understand is that Force X Distance on
the input side of the equation equals Force X Distance on
the output side. This is true for all classes of lever.
Finput x dinput = Foutput x doutput
Mechanical Advantage
Mechanical Advantage.
In choosing the right simple machine to accomplish a task, a
useful metric is the machine’s Mechanical Advantage (MA).
Mechanical Advantage is a measure of how much a machine
amplifies the input or effort force.
For example, if you are only capable of exerting 100 pounds
of effort force, you could not directly lift up a car weighing
3000 lbs one foot off the ground.
However, with the aid of a simple machine (a car jack) you
can push down with your 100 lbs of effort force across a
distance of 1 foot 30 times, and raise the car a distance of 1
foot.
Thus, the MA of this car jack in this case is 30.
SMALLab Learning, LLC
http://smallablearning.com
2
Equation MA
There are two ways to calculate the mechanical advantage
of a device, force it is :
MA = Forceoutput/Forceinput
However for distance is it:
MA = Distanceinput/Distanceoutput
(This equivalence arises from a rearrangement of the
equation Finput x dinput = Fo. This manipulation yields:
Forceoutput/Forceinput= Distanceoutput/Distanceinput , a quantity
that has come to be known as “Mechanical Advantage.”)
Prompt students to explore ratios of output to input force,
input to output distance.
3rd class system
Let’s look at a set of tongs.
Tongs would be considered what class lever? Why?
Where is the input force? Where is the output force?
Can tongs have a mechanical advantage greater than 1?
Why or why not?
(answer No, they can’t, because the input distance will
always be smaller than the output distance, which will yield
an MA < 1)
Let’s explore the MA equation and think about how that
applies to a different class 3 lever system.
This time we are going to use a game called Mars Red Rover.
I need two volunteers. One will be the Driver of the rover
and one will operate the Rock Cracker/Crusher. Then you
can switch roles.
Begin GAME
Be sure and discuss the
difference between crushing
and cracking before they jump
into play!
THE GAME
Before the students start they need to understand that the
crusher gets to decide where along the lever arm to apply
the force in order to accomplish the required task of either
crushing or cracking the rock.
Press space bar to start
countdown
The goal of the game is to collect rocks on Mars. You need
to assess their mineral composition, but depending on the
rocks’ hardness you need to either crush or crack them.
Configuration panel
Hit CTRL C to open the config
panel.
The driver makes the Rover go forward with arms straight
out. Moving the right arm to the right turns the Rover right;
moving left arm further to left, turns the Rover to the left.
Pulling back both arms, like horse reins for ‘whoa’, makes
SMALLab Learning, LLC
http://smallablearning.com
3
You can alter the length of each
game.
You can change the magnitude
of force that will be applied in
the configuration panel up to 99
Newtons – the default force is
10 Newtons.
Hardness
Your students must take into
account the hardness of the
rock in determining the
distance for the input force
values. In the game, hardness is
a random range between 55%
to 95% of maximum output
force, this math is done “under
the hood” for you. It shows up
as an integer in the feedback
box. (e.g., you might think of
force between 55 and 67 as
Soft, 68 to 82 as Medium and 83
to 95 as Hard). If orders from
“command central” are to crush
the Rover slow and then go backwards.
The crusher then confers with the driver about where to
place the force on the levers (there are three points along
the lever arm at which the crusher can apply the force).
The team needs to be careful about the placement of the
applied force because if they apply too much force when
trying to CRACK a rock, it will be crushed and cannot be
collected!
The Force applied by the lever arm is a “preset” that is
entered into the configuration panel. Initially leave the
preset at the default value. As students become more adept
at playing the game, allow them to request the particular
force value that they want preset into the configuration
panel.
If they don’t apply enough pressure to CRUSH rock, what
will happen?
That would also be a mission fail (as in, if the rock remains
intact scientists will be unable to determine the composition
of the rock).
Again, you have a predetermined amount of input force you
can apply to the Rover’s lever arms or pincers. But, you are
in control of where you apply that force, it is the location
that affects the ultimate output force on the tips of this
lever system. There are three different locations where you
can apply force. Close to the fulcrum (with your arms
against your chest), midpoint, or far from fulcrum– at the
tips (with your arms all the way stretched out).
the rock you will never be able
to crack a rock. Hardness on
screen will range from 0 to 80.
Large version of image at
bottom of document
Let’s revisit our equation.
Using trial and error your students will determine when
there is too much pressure.
If their goal is to crack then they need to match half of the
hardness value up to the rock’s hardness value – once the
force has reached or exceeded the total hardness value,
they will crush the rock and fail the mission.
SMALLab Learning, LLC
http://smallablearning.com
4
Sensemaking
Helpful analogy- Barbecue
tongs
One analogy we like to use is that of barbeque tongs. If you
were trying to flip over a heavy steak where would you grab
the tongs? (Nearer the meat-further from the fulcrum.)
What if you had a delicate piece of vegetable to flip? You
only have the same amount of gripping force to apply so the
question becomes WHERE would you apply it – close to the
fulcrum or farther from fulcrum?
For something delicate, you would want to grasp closer to
the fulcrum as this would result in less force applied at the
tips so you so would not crush the vegetable.
Created by: SMALLab Learning, LLC, funded by Next Generation Learning Challenges, Wave II
Last Modified 8/23/12
SMALLab Learning, LLC
http://smallablearning.com
5
Standards: Next Generation Science Standards
Science and Engineering Practices:
Asking questions and defining problems, analyzing and interpreting data, developing and using models,
using mathematical and computational thinking, constructing explanations and designing solutions,
engaging in argument from evidence, obtaining, evaluating and communicating information, planning
and carrying out investigations.
Disciplinary Core Ideas:
Middle School Earth and Space Science – Human Impacts: Human impacts on earth systems (ESS3C).
Middle School Physical Science – Structure and Properties of Matter: definitions of energy (PS3A);
Energy: Forces and Energy (PS3C); Energy Conservation and Transfer: conservation of energy and
energy transfer (PS3B), energy in chemical processes and in everyday life (PS3D); Forces and motion
(PS2A); Interactions of forces: Types of interactions (PS2B).
Crosscutting Concepts:
Cause and effect, systems and system models, energy and matter, stability and change, influence of
science, engineering and technology on society and the natural world.
Common Core Mathematics Standards
MP.2 Reason abstractly and quantitatively.
MP.3 Construct viable arguments and critique the reasoning of others.
MP.4 Model with mathematics.
SMALLab Learning, LLC
http://smallablearning.com
6
6.RP Understand ratio concepts and use ratio reasoning to solve problems.
6.EE Represent and analyze quantitative relationships between dependent and independent variables.
7.RP Analyze proportional relationship and use them to solve real-world and mathematical problems.
7.EE Solve real-life and mathematical problems using numerical and algebraic expressions and
equations.
8.EE Understand the connections between proportional relationships, lines, and linear equations.
8.F Use functions to model relationships between quantities.
SMALLab Learning, LLC
http://smallablearning.com
7