V2
H
INITIAL EXPERIMENT:
This experiment was set up to investigate the aim as stated above:
APPARATUS
Stand and clamp
Plastic, v-shaped track
Three 30cm rulers
Stop clock
Marble (which will represent the roller coaster)
Plasticine
METHOD
The apparatus will be set up as shown in the diagram (shown over page). The height of the top of the v-track will be measured and recorded. A marble will be placed at the top of the v-track and left to roll down it. When the marble reaches the end of the v-track and just begins to roll onto the flat part of the track, the stop clock will be started. When the marble reaches the end of the flat part of the track the stop clock will be stopped, and the time on the clock will be recorded. The experiment will then be repeated two more times at that particular height, and then the height will be changed, and all this will be repeated a further five times.
DIAGRAM
FACTORS NEEDED FOR A FAIR TEST
As the only variable in my experiment is the vertical height, to keep other factors fair, I must use the same equipment. This means that the amount of friction present will be constant. By using the same marble and apparatus, there will be the same amounts of energy being transferred into friction, giving fair results.
If I use the same marble, then the aerodynamics of the marble will not change. As the aerodynamics could vary with different marbles, and cause them to travel faster or slower, my results will be fair and accurate if I keep the marble used constant.
When the speed of the marble is calculated by distance/time, the distance of the track will be kept constant; therefore the only variable will be the time it takes for the marble to travel along the flat part of the track. When the marble is travelling down the plastic v-track, the distance it travels will always remain constant, therefore there will be a set distance for the marble to accelerate in, and therefore the marble’s speed will only vary because of the heights of the v-track, not because it has had different distances to accelerate in.
As the experiment is set up on a flat surface, it cannot accelerate on the flat part of the track. To keep the run smooth, plasticine will also be used to smooth the run from the v-track to the flat surface. This is so the marble does not bounce onto the surface, causing inaccuracy, and would also affect the speed of the marble.
SAFETY PRECAUTIONS
It is essential to complete the experiment with safety in mind therefore, it will be important to wear goggles during the investigation, in case the marble travels out of the experiment area. For the same reason, its important that people are warned before the experiment is performed, so that they can be aware of any possible dangers, and children should not be around the experiment, as small parts such as marbles are hazardous to their health if swallowed.
RESULTS
I aim to obtain results for six separate heights, giving me the speed at which the marble travels at, due to the change of height. The marble will be timed from when it reaches the flat part of the track, until the end of the flat track. The speed can be calculated as below:
The distance that the marble travels is a constant 82 cm. In order to obtain accurate results, it will be important to obtain three results for every height, obtaining an average speed. This should give me a broad range to be able to see any pattern in order to make a conclusion.
I was very satisfied with my results, as they proved my theory. The results to my initial experiment are as tabulated below:
I did not change my procedure for my actual experiment; however, I carried it out with the utmost care and precision, ensuring that the results were as accurate as possible. My results for the actual experiment are as below:
ANALYSING THE RESULTS
The results from my experiments show that as the height of the track increases, as does the velocity of the marble. My graphs both show positive correlation. The data is directly proportional, as the line of best fit goes through the origin. As the height of the track was increased, the velocity of the marble increased too. As the height of the peak of the track is increased the velocity of the marble increases as well. This is because v²=2gh. For the velocity to increase, the height has to be extended; meaning that the figure for height will have to increase in order for the velocity to be greater.
EVALUATION
My prediction and results proved that my experiment was successful, and there were not many anomalies. Sometimes the marble would bounce along the track when it was rolled from large heights; I tried to prevent this from happening by putting plasticine on the part of the run where the two different tracks joined. This still did not always work. Human error will also affect results slightly. This is because the results will include my reaction and thinking times, and unless a computer is used these can never be prevented, however these are insignificant, as they cancel each other out. My results will be in the same proportion though, because for each reading my reaction and thinking time (which normally will never differ) are always included in the final time taken. Another factor, which will make the results slightly inaccurate, is friction. This is because in my equation to show that if you increase the height the speed will increase (v²=2gh) I have assumed that all the energy will be transferred to kinetic energy. However, realistically this will not have happened, as friction will always have been present.
In the 2 lines of best-fit graphs, there were two anomalies, each one for the height of 0.5 meters. I think this happened because as the height of the track increased the marble was more liable to bounce. This caused the time it took for the marble to complete the track to be smaller, which meant the speed of the marble was faster. Even though I had one anomaly for each graph, I still think I had enough results to make a conclusion.
If I had the means, an air track/computer would be used for accuracy.
If I had the time, I would also repeat the experiment more, so I could obtain a more accurate range of average speeds of the marble. I could attempt to ensure that the distance of the track never changed, and the surface level would always be constant- giving me accurate results. I could also ensure that the marble is dropped from the same position on the track by using a marker pen to indicate the position on the track.
EXTENSION: INVESTIGATING THE SPEED OF A MARBLE WHEN THE GRADIENT OF THE TRACK IS KEPT CONSTANT BUT THE HEIGHT OF THE TRACK IS CHANGED
The results of this investigation may be similar to my previous ones. The same method will be used, as before, though when the height of the track is changed, the sloping part of the track will be adjusted accordingly, to ensure that the gradient stays the same, unlike in the initial experiments.
The diagram will also be identical to the one in my main experiment, apart from the gradient being kept constant. I predict that when the height of the track is increased the speed of the marble will increase. This is because in the equation 2gh=v², and since the gradient is not in the equation, it must not affect the velocity. The experiment provide me with more precise results, as in my main investigation the gradient was not kept constant, even though it was not supposed to be a variable. By keeping the gradient constant, the height of the track and length of the sloped track will change. I will collect results using the same range as I did in my main experiment.
The results table shall be the same, but I would add an extra column, labelled the “Length of the Sloped Part of the Track (m)” and record the measurements of the length of the track for each change in height. Afterwards it will be interesting to see how the length of the sloped track has affected the speed of the marble.
I would keep everything identical to my main investigation; all the factors and variables will be the same with the exception of the gradient as a constant. My results will be analysed in a similar way to how my results in the main experiment were. The speed of the marble will be compared to the change in height of the track in order to realise some form of pattern. A graph will be plotted which will have the same format as the ones in my main investigation. Last of all, if possible, a conclusion will be formed, like before.