Lab 06 – Conservation of Energy, Part I Assessment
Directions: Answer the questions below and make sure to upload the completed
assessment and Logger Pro files to D2L by the due date.
Names: (5 points) Now you will determine the spring constant from the weightvs.-position graph. Click Linear Fit to fit a straight line to your data. Record the
best fit equation below.
From Hooke's law the spring force is proportional to its extension from equilibrium,
therefore
𝑭 = −𝒌𝒙 , where
k = spring constant, F = spring force, x = the spring position
From the data collected, we can find the value of k as follows.
Force
(N)
0.392
0.588
0.784
0.882
1.078
1.274
Position
(m)
0.589617
0.5503435
0.5115845
0.492205
0.45276
0.413315
Since in 𝒚 = 𝒎𝒙 + 𝒃 , - k = m then, we can substitute -5.008 in m place. Then the
value of k will be:
-k = -5,
1)
or
k=5
(10 points) Save the Logger Pro file and upload it to the Assessment folder
along with this lab assessment.
2)
(5 points) Based on your analysis of the graph, what is the relationship
between the weight and the position of hanging mass? Use the best fit equation in
Step 1) and determine the spring constant.
From question number 1, we calculate spring constant k from the data
collected, to remind you that:
0.392 - 1.274 = -5.002779= -k, we can approve this value taking any two
points from force or weight and 0.589617-0.413315
any two points from
positions.
The relation between the weight and the position can be determined from the
above data. That is when the force or weight is increasing, then the position is
decreasing. The inverse is also true. When the position increases the force or
weight is decreasing.
(5 points) Click on the -axis label of the velocity graph to choose another column for
plotting. Click on More to see all of the columns. Uncheck the velocity column and
select the kinetic energy and potential energy columns. Click to draw the new plot.
Predict how the sum of the kinetic and potential energies should vary with time if
mechanical energy is conserved in this system.
First let us see the graph of kinetic energy (KE) and potential energy (PE) on
the velocity vs time.
There is a change of potential Energy (change of PE) with respect to different
points of time.
There is a change of kinetic energy (change of KE) with respect to different
points of time.
The sum of the change in kinetic energy (KE) and the change in potential
energy (PE) is equal to zero. Since the total energy will remain the same, when
the potential energy or the kinetic energy changes, the other will also change in
the opposite direction (as PE decreases, KE will increase the same amount to
conserve total energy).
(5 points) 3. Check your prediction. Click on the -axis label of the energy graph to
choose another column for plotting. Click on More and select the total energy column
in addition to the other energy columns. Click to draw the new plot. What do you
conclude from the total energy vs. time graph about the total energy of the system?
When we look the three graphs together, the top one is their sum that show:
𝑷𝑬 + 𝑲𝑬 = 𝑻𝑬
Generally, our predict is proved by the graph. The total energy remains the
same. As potential energy increases, kinetic energy decreases. As kinetic
energy increases, potential energy decreases. All while the total energy is
conserved since there are no non-conservative forces.
3)
(10 points) Save the Logger Pro file and upload it to the Assessment folder
along with this lab assessment.
4)
(5 points) Does the total energy remain constant? Should the total energy
remain constant? Why? If it does not, what sources of extra energy are there or
where could the missing energy have gone? Explain.
The total energy should stay the same, since there are no non-conservative
forces. From the graph, it looks as though the total energy is not perfectly
constant. Some factors that could be affecting this could be non-conservative
forces such as air resistance. Or the beginning energy could have been
manipulated by the push or pull or a person which can add non-conservative
force to the object.