There will be two ways in which I can deliver the wave through the medium. I can either create a to and fro motion wave (longitudinal) or create a side to side wave (transverse). I have chosen to create a transverse wave as it is much easier to see travelling through the slinky.
The above diagrams shows a longitudinal wave travelling through the slinky. These waves are usually too small to see and too fast to distinguish and so I will not be creating this wave type.
The above diagrams shows a transverse wave travelling through the slinky. As you can see, this type of wave is much easier to distinguish.
Safety
There are not any serious safety precautions in this test. However, there are some safety hazards that I will need to be aware of;
- I will need to work on the floor where there is a lot of space and make sure that nobody else is near the apparatus. This way nobody can step on or trip over the apparatus.
- Take special care with the slinky spring as it can be damaged by pulling it wide apart and then letting go.
Fair Test
To make this a fair test I will make sure that I will use the same slinky throughout as some slinkys may have kinks in them or some may be of different weights. These factors may affect the results obtained.
Accuracy
I will carry out this experiment three times so then no obvious mistakes can be made. I will then work out the averages in a separate table and from this table I will plot a graph of wave speed against tension. I will use a slinky spring that has no kinks in it as this will affect the experiment and may give anomalous results.
Precision & Sensitivity
The stop clock has a precision of 0.01 seconds.
The Newton Metre has a precision of 0.1N.
The sensitivity of the measuring tape is not very good because the scale is in inches, metres or centimetres. Therefore, to measure accurately I will have to guess the measurement if it is not exactly a whole centimetre. Due to lack of apparatus a tape measure of greater sensitivity cannot be used.
The timer that I will use has a very high sensitivity and good precision. The clock measures time to the nearest hundredth of a second which I think is quite accurate for this experiment.
The Newton Metre that I am going to use will have god sensitivity and precision because I will be increasing the tension by 0.5N each time so a precision of 0.1N is good.
Theory
From my scientific knowledge a wave is a disturbance that travels along a medium from one end to the other. I can say that the speed of a wave depends upon the properties of the medium through which it is transmitted. The factors that effect wave speed are the tension of the medium and the mass density of the medium. The medium in this case is the slinky spring. The amplitude and the frequency of a wave do not affect the wave speed. The theory to be stated is:
“As the tension of a medium is increased so will the wave speed”
After I have obtained my results I will plot a graph to see if this theory is correct.
Observation
The results have been recorded in the table below. As explained earlier, I repeated this experiment three times and so have three different time recordings. Hence, I have taken the average of these time recordings in order to plot a graph.
The values that have been highlighted in green create an anomaly. This can be seen on the graph.
Analysis
The graph below has been plotted with respect to wave speed against tension.
The graph above clearly shows that as the tension of the slinky spring is increased then the speed of the waves travelling through it will also increase proportionally. A line of best fit (a curve) is drawn which shows tells us that the points have a strong positive correlation, however, there is one obvious anomaly that is some distance away from the curve.
There are some reasons why I may have obtained an anomaly such as:
- I may have sent a larger amount of energy down the slinky, therefore an increased wave speed
- My partner may have stopped the timer slightly quicker than was supposed to.
- The slinky may have a kink(s) in it.
The percentage error of this anomaly is 1.32 / 7.52 X 100 = 17.5% error. This is a huge amount of error so it most likely would have been caused by one of the bulleted reasons stated above.
Evaluation
I conclude that the theory that was to be tested it correct. As the tension in a slinky is increased so does the wave speed proportionally. From analysing the graph I can say that this experiment was not very accurate as I had one obvious anomaly. However, the results still agreed with the theory. The points are spread out and are on or near the line of best fit (excluding the anomaly).
The main reason for me saying that this experiment was not very accurate is because I had to create a wave myself and to make this experiment fair I had to use the same amount of pressure for creating a wave movement each time. This obviously cannot be controlled to an exact pressure which will be used, however, a rough estimate was used. This could have caused me to have the anomalous result in my observations.
If I was to do this experiment again I would use a tape measure that has much better precision as it is more practical to use. This would limit the number of anomalous results. Also, I could make sure that I will use the same amount of pressure on creating a wave each time. This is a major factor that has to be considered to make the experiment a fair test.
