Investigation Into How the Depth of Water Affects the Speed of a Wave
INVESTIGATION INTO HOW THE DEPTH OF WATER
AFFECTS THE SPEED OF A WAVE
Aim
To find how the depth of water affects the speed of a wave.
Waves are vibrations (or oscillations) moving through something - a
medium. As a wave passes, each bit of the medium vibrates in turn. The
vibrations appear to move through the medium. Each bit of the medium in
turn vibrates/oscillates, but stays where it is. The wave transfers energy as
it moves. The medium can be matter (solid, liquid, gas). This is the case
for water waves.
There are two types of wave:
a) Transverse waves. The vibrations are at right angles to the direction of
the wave.
b) Longitudinal waves. The vibrations are along the same direction as the
waves.
The waves I will be studying are transverse waves.
During a previous experiment I found that a drop height of 5cms and to
allow the wave to do 3 laps of the container before stopping the
stopwatch was the best course of action. 5cms is a good height because it
is high enough to cause a strong wave, but not high enough to create water
to spill over the container's edge. I chose 3 laps because after that the
wave starts to lose momentum and slows down.
Apparatus
Container
Stopwatch
Ruler
Water
Prediction
I predict that the greater the depth of water, the faster the waves will travel.
The reason for this is that when the water is shallow, the container bottom
begins to interfere with water motion. The bottom constrains the water
motion and results in a dragging affect on the waves. Also, the deeper the
water the greater the mass and therefore force of the wave, which creates
more momentum and speed. I have chosen the depths ...
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Apparatus
Container
Stopwatch
Ruler
Water
Prediction
I predict that the greater the depth of water, the faster the waves will travel.
The reason for this is that when the water is shallow, the container bottom
begins to interfere with water motion. The bottom constrains the water
motion and results in a dragging affect on the waves. Also, the deeper the
water the greater the mass and therefore force of the wave, which creates
more momentum and speed. I have chosen the depths 0.2cm, 0.5cm,
cm, 2cm, 3cm, 4cm, 5cm, 6cm, 7cm, 8cm, 9cm and 10cm because they
will show a large range of results.
Method
) I will fill the container with 0.2cm of water, measuring it using the ruler.
2) I will hold the end of the container firmly and lift it to a height of 5cm,
which will be measured using the ruler.
3) I will drop the container.
4) Using the stopwatch, I will measure the time taken for the wave to
complete three laps of the container.
5) I will repeat this experiment with depths of 0.2cm, 0.5cm, 1cm, 2cm,
3cm, 4cm, 5cm, 6cm, 7cm, 8cm, 9cm and 10cm.
6) I will repeat the complete experiment ten times to verify my results.
To make the experiment fair I will only change the depth of water, all other
variables such as the size of container used, which would corrupt my
results will stay the same. I shall also make my results fair by doing
accurate time keeping and making sure that the container is dropped from
the same height each time. For each drop I shall make sure that I stop the
stopwatch when wave has. For safety reasons I will make sure that the
container does not fall on my hands. I will repeat the experiment ten times
to make sure that my results are conclusive and any anomalous results are
noticed easily. It will also allow me to find an average for my results.
Conclusion
As I predicted, the greater the depth of water, the faster the waves travel.
This is can be seen clearly in my results as the depths of 2cm, 3cm and
4cm which recorded times of 3.45s, 2.95s and 2.67s respectively. It can
also be seen when looking at the difference between the times recorded by
the lowest and highest depths, which is 5.98 seconds. The reason for this
is that when the water is shallow, the container bottom begins to interfere
with water motion. The bottom constrains the water motion and results in
a dragging affect on the waves. Also, the deeper the water the greater the
mass and therefore force of the wave, which creates more momentum and
speed. My results support this explanation totally.
Evaluation
The experiment itself was successful, I know this because the results
found were what I would have expected and followed a strong pattern.
For the same reason I think that if I repeated the experiment I would find
the results would follow the same pattern, and the times would be
extremely similar. The experiment was relatively accurate, however it was
impossible to say exactly when the wave had reached the edge of the
container. It was also hard to measure precisely 5cm from the table to the
container when dropping, as my hand was prone to moving before the
container was released. I was very careful to make sure that the depth of
water was as accurate as the apparatus allowed and stopped the
stopwatch as close to the moment when the wave competed it's final lap
as I could.
I did observe one anomalous result, attempt 9 at a depth of 8cm when the
wave was timed taking 1.80 seconds. This was not consistent with the
other results taken for that depth and so was re-timed, giving a more likely
time of 1.69 seconds. The anomalous result was most likely due to either
the stopwatch being started before the container had been dropped, or the
container being dropped at the wrong height.
Yet I did observe the results I expected, had only one anomalous result
and followed the rules of my plan making it as fair a test as possible. My
investigation was conducted safely and without any setbacks. I therefore,
considering the above, believe my experiment was fairly accurate but
could be improved upon by considering the previous points.
To expand and improve upon my investigation I could : -
* Wedge a level object under the container and remove it from underneath
to drop the container. This would determine that the dropping height
remained constant.
* Use a wider range of depths.
* Use more accurate apparatus for measuring time and distance.
All of these would enable me to make more detailed and accurate
conclusions.
Ultimately I think my initial plan was suitable, giving the time and apparatus
available to me, but could be improved or expanded upon by considering
all of the above.
Mark Seddon 11B
