Spring Potential Energy
Lab 6
In this experiment we will attempt to confirm energy conservation. A
mass that compresses a spring will have potential energy associated
with it. That potential energy is converted to kinetic energy as the
mass is accelerated.
m
mTotal Mechanical Energy
We will show that energy is conserved by comparing the initial total
mechanical energy to the final.
m
mTotal Mechanical Energy
For this experiment you will use the short
spring and the iOLab device. You will first
measure the mass of the iOLab and then
spring constant k of the short spring. You
will then compare the spring potential
energy while the spring is compressed by
the iOLab by using the iOLab to measure
the compression, to the kinetic energy by
using the iOLab to measure the velocity.
Demonstration Video
https:
www.youtube.com/watch?v=ELLk7WrYuHg
1. Attach the hook to your iOlab. We will now measure the actual mass of the device. We
will do this by picking the mass up and holding it steady, then measuring the applied force
on the object as it balances out gravity.
m
Part 1a – Finding Mass of iOLab (skip if you have done
this in previous experiments)
2. As always, first Cali
ate both the
accelerometer and the force sensor.
3. Choose the Accelerometer Sensor
and select Ay.
4. Select the Force Sensor.
5. Click Record, then pick up the device,
hold it for a second or two, then set it
ack down and stop recording.
6. Zoom in on the constant non-zero
applied force after you have picked up
the mass and before you set it down.
7. After zooming in, highlight a section of
the graph. Your graphs should now look
like...
...this.
8. Write down the average acceleration As your object is at rest, your device is
directly measuring the acceleration due to
gravity and not the actual acceleration.
9. Write down the average force.
10. Now calculate the actual mass of the device by...
Include this value in your report.
Part 1b – Measuring the spring constant of your spring.
We will calculate the spring constant of the
spring by measuring the applied force from
stretching the short spring while attached to the
mass as well as the displacement.
Spring constant
Displacement
from Equili
ium
1. First Cali
ate both the accelerometer and the force sensor.
2. Select the Force Sensor. Select the Wheel Sensor, and highlight only the
position setting.
3. Select the Parametric plot mode. Make sure that Force is on the y-axis
and Position is on the x-axis (otherwise click Swap axis).
4. Click Record. Hold the end the spring firmly in one hand, and do your best not to move
from that position. With your other hand, stretch the spring by pulling the iOLab device back
and forth at a slow-to-moderate speed (wheels down), increasing the total displacement each
time. After a total of 4-6 stretches stop recording. Be gentle with your pulls as the shirt spring
is somewhat easy to warp.
5. Highlight a portion of the graph on the bottom after you began
stretching and relaxing the spring, but before you stopped applying
force to the spring. This should populate the graph above.
Wheel Position (m)
Fo
c
e
(N
)
6. This should reveal a mostly linear graph (the outliers are likely data
etween stretches and do not apply). To the best of your ability calculate the
slope of this line using the positions on the grid. Mark this as your
experimental spring constant k. Include this and a screen grab of your
graph in your lab report.
Wheel Position (m)
Fo
c
e
(N
)
Part 2 – Conservation of Energy
1. First Cali
ate both the accelerometer and the force sensor.
2. Attach the short spring the the iOLab device.
3. Select the Wheel Sensor, and highlight only the position and velocity setting.
4. Select Record. Gently compress the spring connected to the iOLab into a wall
with the iOLab’s wheels down on a smooth surface as in the picture below.
5. Allow the mass to accelerate away from
the wall, then stop recording data.
6. The data on the position versus time graph here shows the compression of the
spring (the figure to the right is zoomed in). This depth is the XXXXXXXXXXvalue.
7. Calculate the initial potential energy the mass has from compressing the spring.
Include this in your report.
Where the
spring is
maximally
compressed.
Where the
mass is
accelerated by
the spring.
Where all of the
potential energy
is converted to
kinetic energy.
8. Examine the velocity versus time graph. Write down the maximum value, this
should co
espond to when the potential energy from the spring is converted to
kinetic energy.
9. Calculate the final kinetic energy the mass has after leaving the spring. Include
this in your report.
m
mTotal Mechanical Energy
10. Calculate the initial total mechanical energy when the spring is compressed.
Write this as in your report.
11. Calculate the final total mechanical energy when the has the maximum velocity.
Write this as in your report.
m
m
12. Calculate the percent difference between the initial and final potential
energies. Include this in your report.
13. Consider the sources of uncertainty in your experiment. It’s likely that the imprecision
your measurement of your spring constant is the largest source. Revisit your force versus
position graph from Part 1b. Estimate the steepest reasonable kupper and the shallowest klower
ased on the noise in your data.
14. Recalculate your initial total mechanical energy with each kupper and klower (step 10), then
the percent difference (step 12). Note the range of percent differences in your report.
15. Compare your results with your lab partners, specifically but not exclusively, the mass of
the iOLab, the spring constant, and the percent differences found in your measurements.
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