Before taking any readings of the wave velocity I will measure the length and width of the tray and also see if the tray is flat on the bottom and along the sides. I will do this by placing 1cm depth of water into the tray, taking the measurements at either end and in the centre of the tray. I will then begin the experiment.
- Set up apparatus as shown in the diagram.
- Fill the tray with water at 5mm intervals
- Place the support tray underneath the tray (measured to be a height of 13mm) and gently remove it so the tray is dropped and a wave is generated
- As soon as the stand is removed, start the stopwatch timer. Count the waves till it makes 4 trips end-to-end and stop the timer when it does so.
- Record the results in a results table and do this another 2 times to ensure a fair test
- Repeat for each 5mm depth interval to a limit of 40mm
The potential health and safety risks of this experiment are spilling the water contents on the floor or near any electrical appliances.
This can be avoided by careful handling.
If this problem was to arise, then the water must be wiped up immediately.
Length of tray - 40.50cm
Height lifted to – 13mm
During the experiment there were a few factors that could have potentially affected the results:
1. The waves curved at edges which means not all of the wave reached the end of the tray at the same time.
2. When I increased the depth of the water a small amount of the water spilled over the side after the tray was dropped.
3. The tray was risen a couple of mm in the middle and so could have caused a minor difference.
By using the formula (Vmax – Vmin) ÷ 2, where V is the velocity, I can work out the limits of experimental uncertainty and plot error bars with my results onto the graph.
* data is an outlier/anomalous compared to the others but will still be included, hoping it does not have much affect.
With my standard results I have plotted a graph of velocity (V) against depth (D). However this showed only a small trend and a curve of best fit had to be drawn, showing that there is no direct proportionality. This isnt as I originally predicted.
To be able to achieve a relationship between the velocty of the waves and the depth of the water, I have tried plotting V² and √V to see what kind of trend I was able to distinguish.
I found that the suare root of the velocity produced a graph similar to the original, leaving a curve of best fit with a slight trend in results.
I managed to find that the depth of water against the velocity of the wave squared produced a straight line, however did not pass through the origin by a small amount. This shows that the depth of water is directly proportional to the velocity squared only as proven satisfied pass the origin.
V² is directly proportional to Depth
Hence Therefore: V is directly proportional to √Depth
The straight line shows that wave velocity increases proportionally with √Depth. Where there is a greater depth of water, the water has a greater mass and so, by conservation of energy, when it has a higher mass and height it will have a greater kinetic energy when dropped.
The increase in velocity begins to slow down with a greater depth as it has a greater surface area in contact with the tray; therefore, there is a greater amount of friction. The greater the friction, the quicker the kinetic energy decreases.
If I were to carry out this experiment again, I would make the following improvements/changes:
- Use a deeper tray so that it can be raised to a reasonable height without splashing over the sides slightly.
- I could investigate in a greater range of depths which could also increase the reliability of my results.
- Investigate other factors that may vary a waves velocity.
AS Advanced Physics Salters Horners Heichemann, 2000
Here's what a teacher thought of this essay
A graph would definitely improve this report but the general approach to gathering data makes sense on first reading. The results are consistent with theory. Some further comments about uncertainties with the timing and measurement of depth could have been included. Overall a good report but missing key information. 3 stars