Name:
Work & Energy Inquiry Lab
Honors Physics
Introduction: This lab is a multi-part lab that will let you investigate many different
concepts in work & energy. Ultimately, you will be looking to find two major new
relationships/laws.
Part I: In this lab you will be using a spring-loaded Vernier Dynamics Cart. Before we can
go any further we need to find the spring constant of the cart’s spring. In the space
below, show your work to find the spring constant k:
You must use this graph to get valid results
k= _____________________N/m
Review: What equation will let you find the work done to compress a spring, and where
did that equation come from?
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Part II: The goal of this section is to find a relationship between the work done on the
cart’s spring and the resulting velocity of the car. Again, we will use graphing to find this
relationship
Step 1: Predict the relationship between work and velocity by drawing it on the graph
below:
Wα
Step 2: Experiment to find the actual relationship between work and velocity. Fill in the
data table below.
Wα
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Equation relating work and velocity (specific to your graph):
What do you think your slope represents? Test this out
Concept question: What would the graph look like if you used the spring to stop the car
rather than launch it? Draw your predicted graph on the axes below:
You should have found a relationship between work and velocity that is equivalent to
the work-energy theorem. Ask Mr. O’Dell for a copy of this theorem and answer the
questions below:
1. Are your results consistent with the work energy theorem?
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2. If you double any of the following quantities, what effect would it have on the
resultant velocity? Give some specific examples from your data table to prove it.
a. Doubling force
b. Doubling work
c. Doubling compression of the spring
d. Doubling the mass of the car
3. Using the terms work and kinetic energy, describe what would happen to the car
if it was moving and hit the track’s end stop spring side first. Make sure you
account for the cart’s energy at all times.
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Part III: In part II you should have found a relationship between work and energy. But
what happens to that energy? That’s the question you’ll be answering in this section.
Let’s start with a couple predictions/ideas:
1. You’re doing work when you compress the spring in part one. That means you
are using up some of your energy. Work is supposed to be a transfer of energy.
Where is the energy that you “used up” when the spring is compressed (before
you release the car)?
2. Use the rod clamp to raise the ramp to a 100 angle. Use the spring to launch the
car up the ramp. What happens to the kinetic energy that the car had at when it
was launched?
3. Predict a relationship between the initial velocity of the cart and the height it can
reach. Use a graph to show this relationship.
4. Ask Mr. O’Dell for the “types of energy” sheet. Give an example of when the cart
has each of the following types of energy:
a. Kinetic energy
b. Gravitational potential energy
c. Elastic potential energy
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Investigate: You’re on your own to investigate what’s going on with the cart’s energy.
You should, from your knowledge of work and kinetic energy, be able to make some
predictions about energy transformations. In the space below, write down some
predictions and then show how you tested them. At the end, you should be able to draw
a broad conclusion about the energy of a system like the car on the dynamics track.
What did you find out about energy as the cart is launched up and down the ramp? Give
specific examples that describe how and when the object has different types of energy.
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Post-Lab Analysis:
When physicists analyze “work”, they group forces into two categories. Conservative
forces do work that changes the energy of an object from one form to another, but they
do not change the total amount of energy. Non-conservative forces do change the total
amount of energy in a system. In this lab our “system” is the cart and spring, so we need
to look at if the total energy of the cart/spring combo is changing or not.
These should be typed or neatly hand-written on a separate sheet of paper.
1. Identify four different forces present in this lab and decide if they are
conservative or non-conservative. Give some evidence:
2. Conservative forces get their name because they “conserve” the total energy of
the system. Give two examples of when you could use the conservation of
energy to find out some useful information.
3. Define energy in your own words, without using the word “work”.
4. Describe some other way you could test your conclusions from this lab to see if
they apply to different scenarios.
5. Did you learn from this lab? Let me know if you like learning this way or prefer
something else.
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LabQuest Instructions
Force Sensor Instructions:
1. Plug the force sensor into the CH1 port on the LabQuest.
2. Zero the force sensor by going to the “Sensors” Menu and selecting “Zero”.
3. Press on the force sensor and check that you get a positive reading. If not, go to
Sensors -> Reverse to change the sign.
4. You can now get instantaneous force readings on the first tab, a graph on the
second (Be careful – this graph is force vs. time not force vs. displacement), and
a data table on the third tab.
Photogate Instructions:
1. Set your photogate up so that it will measure the cart’s velocity when it is at a
maximum.
2. Plug the photogate into the DIG1 port on the side of the LabQuest.
3. Check that the photogate is at the proper height. It should be catching the small
black markings on the cart’s picket fence. Use the red light on the photogate to
check this.
4. Check that the photogate is in the proper mode. On the first tab, you should see
“Mode” and “Timing” on the right side. Tap here and verify the following
settings:
 Mode: Photogate Timing
 Photogate Mode: Motion
 Select “Vernier Picket Fence”
5. Press play to start collecting data when you are ready to launch your cart. Your
photogate should automatically stop collecting data when the cart is through the
gate. If not, press the “play” button again to stop it.
6. Go to the data table and find the velocity column. Look for the highest reading
and record this as your velocity.
If a sensor does not appear on your LabQuest when it is plugged in, go to the “Sensors”
menu and choose Sensor Setup. This menu lets you tell the LabQuest where the sensors
are plugged in.
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The Work-Energy Theorem
The Work-Energy Theorem says that the work done on an object will be equal to the
change in that object’s kinetic energy.
𝑊 = Δ𝐾𝐸
The Work-Energy Theorem
The Work-Energy Theorem says that the work done on an object will be equal to the
change in that object’s kinetic energy.
𝑊 = Δ𝐾𝐸
The Work-Energy Theorem
The Work-Energy Theorem says that the work done on an object will be equal to the
change in that object’s kinetic energy.
𝑊 = Δ𝐾𝐸
The Work-Energy Theorem
The Work-Energy Theorem says that the work done on an object will be equal to the
change in that object’s kinetic energy.
𝑊 = Δ𝐾𝐸
The Work-Energy Theorem
The Work-Energy Theorem says that the work done on an object will be equal to the
change in that object’s kinetic energy.
𝑊 = Δ𝐾𝐸
The Work-Energy Theorem
The Work-Energy Theorem says that the work done on an object will be equal to the
change in that object’s kinetic energy.
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𝑊 = Δ𝐾𝐸
Types of Energy
Kinetic Energy (KE): Energy associated with motion of an object. KE=½mv2
Potential energy is energy stored in an object as a result of motion against a resisting
force.
Gravitational Potential Energy (PE): Energy an object has when it is lifted a certain height
above the ground, or against gravity.
PE=mgh
Elastic Potential Energy (EPE): Energy stored when a spring is compressed or stretched.
EPE=½kx2
Think of potential energy as energy that gets stored up when an object is in an unstable
state. Objects will fall if they’re above the ground, and springs will “spring back” when
they’re not at equilibrium. There needs to be energy stored up so the object can move
and gain KE.
Types of Energy
Kinetic Energy (KE): Energy associated with motion of an object. KE=½mv2
Potential energy is energy stored in an object as a result of motion against a resisting
force.
Gravitational Potential Energy (PE): Energy an object has when it is lifted a certain height
above the ground, or against gravity.
PE=mgh
Elastic Potential Energy (EPE): Energy stored when a spring is compressed or stretched.
EPE=½kx2
Think of potential energy as energy that gets stored up when an object is in an unstable
state. Objects will fall if they’re above the ground, and springs will “spring back” when
they’re not at equilibrium. There needs to be energy stored up so the object can move
and gain KE.
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