DISCUSSION:
In this experiment, it was observed that as more salt was added,the density of water increased.
A trend in the results was also observed, that is, as the mass salt added increased, the time
for the cylindrical container to make 10 oscillations also increased. Therefore, the denser the
water became the less frequent oscillations were made by the cylindrical container. This is seen
when the value of density increased from 1.00 gcm-3 to 1.112 gcm-3, the time of oscillation
increased from 0.647s to 0.928s. However, as the density of the water increases, the frequency
of oscillations of a buoy is expected to increase as well.
The difference in the experimental results and the expected results may have been due to the
conditions the experiment were executed in. From the graph, the gradient was found to be -5.35
s/g⁻ ¹cm³. This negative gradient implies that the denser the solution the less oscillations the
buoy would experience. This result is inconsistent with the theoretical equation as shown above
where f increases with density.This difference can be due to the solution of the denser mixture
not being homogeneous. The salt may not have been properly dissolved effectively increasing
the density of the solution.
Furthermore, the oscillations may not have been completely vertical so the timing may not have
been accurate.This showed an inversely proportional relationship whereby as the period
decreased, the square root of 1/density increased. As T is equal to 1/f this implies that
frequency should be inversely proportional to the square root of density. In the experimental
data it was seen that the time taken for 10 vertical oscillations increased as more salt was
added to the solution.
To ensure accuracy of the experimental results, several techniques were implemented to
reduce errors. The experiment was repeated and averaging the results helped reduce the
chance of random errors. Additionally, the saltwater was thoroughly mixed to ensure a uniform
solution was formed before measurements were taken. These actions increased the
consistency of results and allowed for a more reliable comparison of how salt concentration
affects the oscillation frequency.
However, sources of error persisted such as delayed reaction time when starting and stopping
the stopwatch. This could have caused slight inaccuracies in timing, potentially affecting the
comparison between saltwater density and the buoy’s oscillation frequency. Moreover, damping
is caused by the resistive forces/drag forces of the water. This force acts opposite to the
direction of motion, causing losses in energy causing amplitude to slowly decrease over time.
This may affect the natural frequency obtained in these results and cause the buoy to take
longer to reach rest position.
When the natural frequency corresponding to a given water density was found, the buoy was
observed to oscillate with maximum amplitude when this frequency matched the wave
frequency. This principle resonance allowed buoy to harness the maximum possible energy
from wave motion.
This finding has many real-life applications. Designing buoys for different ocean regions
requires the knowledge of local water densities, as each ocean's salt content varies.
Understanding how density affects natural frequency allows engineers to calibrate buoys to
achieve resonance and generate power efficiently. As a result, more efficient energy-harvesting
systems can be developed for use in oceans around the world.
Studies such as the Master’s thesis in Ocean Engineering at Rhode University demonstrate the
application of linear electric generators (LEG) in oscillation powered systems. These systems
use the vertical motion of buoys in the oceans, caused by waves, to drive movement between
the buoy and a mounted magnetic armature. This movement allows the generation of electrical
energy.
In order for resonance to occur, the buoy must be calibrated to match the natural frequency of
wave motion at a specific location. The LEG system achieves this by using a sealed buoy
connected to a magnetic float and a calibrated resistance platform. This design includes a
spring system that restores the buoy to its equilibrium position, enabling continuous resonance
in a range of wave conditions. This model expands energy capture potential and increases the
accuracy of wave energy prediction.
By replicating this on a smaller scale in the conducted experiment, a student can better
understand wave dynamics and water density contributing to the real-world development of
renewable energy solutions. Accurately determining the natural frequency of buoys ensures that
maximum energy can be harvested in varying densities of oceans.
PRECAUTIONS:
1. The procedure was repeated 3 times and the average time for 10 vertical oscillations
was calculated in order to decrease the chance of any random errors occurring.
2. The saltwater mixture was stirred frequently with each 60g of salt added to ensure that a
homogeneous mixture was achieved before the period in which the 10 vertical
oscillations of the can was recorded.
SOURCES OF ERROR:
1. The 10 vertical oscillations in this experiment might not be accurately measured as
starting and stopping the stopwatch is affected by the delayed reaction time of the
operator.
2. There may be a loss in transfer of the mass of the 60g of salt to the volume of water in
the tub each time salt is added. This causes the density of the saltwater mixture to vary
slightly, which would affect the time it takes for the 10 vertical oscillations and
consequently inaccuracies may occur.
3. Distilled water was used to ensure that the density was not affected by any impurities,
causing any inaccuracies if repeated.
LIMITATIONS:
1. The water’s temperature may have affected the water’s density and the buoy’s
behaviour.
2. The cylindrical container and the plastic container differ from the scale of the ocean and
an actual buoy which may have affected the accuracy of the results.
3. The oscillations made were difficult to observe which may have affected the accuracy of
the results.
REFLECTION:
Buoys are important for maritime safety, navigation, and can be revelational in harnessing the
energy of the sea. From the statement, buoys use the concept of the wave motion to convert
mechanical energy to electrical energy. In order to obtain the maximum amplitude of oscillation
of the buoy, which would give the most energy, the natural frequency of the buoy must be
known. The density of water is different for different oceans which affects the natural frequency
of the buoy’s movement.
From the experiment, it was observed that higher-density water resulted in lower oscillation
frequency. In day to day life for a student, this information can be applied to swimming. As the
density of the water increases the buoyancy of the buoy increases thus swimming in sea water
will be much easier than freshwater. This will impact decisions made when taking trips with
people who cannot swim well (especially elderly people and young children) as salty sea water
at a beach is better than a fresh water river. For example, the Dead Sea, one of the saltiest
seas in the world, is a very popular destination for the elderly as it is extremely easy to float and
enjoy a leisurely swim.
Additionally, buoys in denser oceans need to be redesigned to account for slower oscillations.
Understanding the effects of salt on the density of water helps engineers in renewable energy
design create buoys for different environments to harness as much energy as possible.
Harnessing the power of the sea efficiently by understanding how density affects maximum
oscillation can assist countries to burn less fossil fuels (especially islands like Trinidad and
Tobago with access to turbulent waters like the atlantic ocean)
With the buoy used in this experiment, less dense water would supply more energy. An
improvement in the experiment would be using a ruler to properly measure the displacement of
the buoy in order to have consistent values.
CONCLUSION:
The inverse of the square root of the density of seawater was found to be directly proportional to
the inverse of the frequency of oscillation of the waves. Thus, the original hypothesis was
disproved as the density of seawater was not directly proportional to the frequency of the
waves.
Therefore, oceans that contain high concentrations of salt have a high density and will not have
buoys with higher natural frequencies than those found in oceans that contain less salt.