By altering a the heights of the ramps and releasing the trolley down the ramp we get an indication of how far the trolley is likely to travel and we can see if there is a link between the height of the ramp and the stopping distance of the trolley. We experimented with 9 different ramps ranging from 5 – 45cm.
To get my results, I will use a ramp height of 5cm throughout my first Preliminary work and the trolley with the same mass. I will let the car travel down the ramp 3 times; each time I will take note of the Braking Distance (remembering to measure at the back wheels of the car every time).
Result
From the preliminary experiment it was possible to conclude that the optimum height for each measurement will vary. This will result in a range of relevant data.
Scientific Knowledge:
- Gravitational Potential Energy (G.P.E.) is the energy possessed by any object that can fall. E.g. when you hold a ball in the air, it has potential energy. The higher the object is, the greater this potential energy is. This potential energy is calculated by the equation:
Gravitational Potential Energy = Mass X Gravity X Height
From this equation, I can deduct that the height of an object definitely affects the overall potential energy because mass, gravity and height all combine to give potential energy. Therefore, if mass and gravity stay the same, but height increases, the G.P.E. will be greater.
- When an object is falling, its G.P.E. is converted into kinetic energy.
- Kinetic Energy is the energy possessed by any object that is moving. This energy depends on the mass and speed of the object. The greater the mass and the faster it’s going, the greater the kinetic energy will be. This kinetic energy is calculated by the equation:
Kinetic Energy = ½ X Mass X velocity²
- In this experiment, as the trolley is rolling down the ramp from a certain height where it has G.P.E. to a height where it has K.E, the G.P.E. at the top of the runway should equal the K.E. at the bottom. This equation can be used to work this out:
Maximum kinetic energy = maximum gravitational potential energy
½ X mass X velocity² = mass X gravity X height
- Velocity, measured in m/s, is how fast an object is moving. It is calculated by the equation:
Velocity = Distance
Time
- Friction is a force, which acts, in the opposite direction to movement. It is always present. E.g. there is friction between the tyres of a car and the road surface. As speed increases, friction also increases. E.g. the friction between the wheels of the trolley and the runway will be much greater at 60mph than at 30mph.
- Gravity is the reason that the trolley is rolling down the runway. This force is acting as acceleration and is always 9.81m/s².
Variables
In order to produce a fair test and allow for comparison of results to occur, there will be only one variable in the experiment. This variable will be the height of the ramp. If anything else is varied there can be no connection made between results because you will not be seeing what the effect of height would have. To be able to investigate how height affects stopping distance only the height of the ramp must be changed and the stopping distance measured. Obviously, factors such as gravity and air resistance cannot be altered, so there is no point worrying about it.
To produce a fair test the many possible variables must be controlled and kept constant so they do not have any effect on results obtained.
Independent Variables:
- Mass / weight of trolley – Mass is present in the formulas for acceleration, force, potential energy and kinetic energy. Therefore any change in the mass of the trolley will affect the outcomes of these equations.
- Gradient of the slope – This depends on the height of the ramp. This is the factor that I will be investigating to see how its effects affect the braking distance.
- Length of slope – The longer a trolley has to roll down the runway, the quicker is the possibility of reaching its peak speed.
- Different surfaces (friction) – The friction between the wheels of the trolley and the surface of the runway will use up some of the energy from the trolley that it is being converted to kinetic energy.
- The point on the wooden plank where the trolley is released – The trolley has to be released from the same point on the wooden plank to keep the experiment a fair test.
- The units of measurement used – If different measurements are used for each experiment then the overall conclusion will be biased.
- Gravity – This factor is hard to change unless you go to a different planet, but it is still an independent variable because it is used in the equations for potential energy, acceleration and weight. Therefore, any change in gravity will affect the values for these equations.
- Air Resistance – Again this is hard to change and its results are virtually insignificant anyway. The main way to avoid changing this would be to use the same trolley.
Factors affecting the experiment:
- The wheels of the trolley used will produce friction reducing the trolley's kinetic energy
- The material used for the ramp will play a role in friction produced
- The shape of the trolley will produce air resistance when it is moving
- The position the trolley is released from will have to be the same for each experiment
Measurements:
The ranges of measurements I plan to use for the heights of the ramp are:
- 05 cm
- 10 cm
- 15 cm
- 20 cm
- 25 cm
- 30 cm
- 35 cm
- 40 cm
- 45 cm
The reason for this is because that they are reasonable heights to use. The numbers of measurements I will do are 3 for each height. This is a logical amount of measurements for the time of which the experiment has to take place within.
Repetitions:
The repetition of results is crucial to gain the best and most accurate results. The experiment will be repeated 3 times, for each of the heights, and an average will be taken, so that if any anomalous results occur then it will not affect the outcome as much as if only 2 recordings were taken for example.
Apparatus:
- 1 metre wooden runway
- 9 ramps
- Trolley
- Marker pen
- Metre stick
Method:
- 1. Set the height of the ramp (Ranging from 5 – 45 cm)
- 2. Place the wooden runway on the appropriate ramp.
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3. Roll the trolley down the ramp 3 times for each height.
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4. Mark where the trolley stops
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5. Measure the distance form the end of the runway to the stopping point of the trolley to indicate stopping distance.
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6. Record the results produce a table and draw a graph to identify trends.
Safety
As with all experiments, safety is an important issue to make sure that nobody is hurt and nothing is damaged.
- Basic lab rules will be followed at all times throughout the experiment such as not running.
- The most important safety issue to note is that the runway should be stable so that it doesn’t collapse and injure anybody or damage equipment.
- Someone will ensure there is no possibility of the trolley going off in inappropriate directions.
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Most importantly is common sense. If the experiment is carried out responsibly, there will be no problems, but if there is foolish behaviour in the lab, there could be accidents.
Reliable Evidence:
To collect reliable evidence we will:
- Take three readings of each height. This is so that any data that seems to be anomalous can be retaken. E.g. if the highest reading differs to the lowest reading by more than 10%, we will collect more data so that the data is reliable.
- Collect data from many heights so that when we come to draw graphs, they can be drawn accurately.
- Not push the trolley or exert any force on it when it is released from the starting point.
(2) Skill Area O: Obtaining Evidence
Recording the Results:
To make this investigation successful, we must choose a sensible range, and amount, of readings to record in order to come up with accurate set of results. It would be pointless to experiment with heights ranging from 1cm-4cm because series of data would be small in order to show trends. I have chosen a range of 5cm - 45cm giving a better variation. We are going to release the trolley three times for each height. Also, another thing, which will help us to get accurate results, is our choice of apparatus. To measure the stopping distance of the trolley more accurately, we are going to measure the braking distance from the end of the runway to the back wheels of the trolley using a 1m ruler. In doing so, our results will be consistent. We recorded the results into the table and repeated each result 3 times. Once we had obtained the results containing the stopping distances, we worked out the averages to 1 decimal place. Working the averages out to one decimal place gave us results which were accurate enough, and which we could easily plot onto a graph.
Results taken from the 1st, 2nd and 3rd experiment:
Average times:
118+122+126=366/3=122
168+172+162=502/3=167
210+218+220=648/3=216
247+251+259=757/3=252
282+290+288=860/3=287
321+328+322=971/3=324
363+368+351=1082/3=361
408+390+400=1198/3=399
438+431+429=1298/3=433
Table Displaying the Average Results:
Here is a table showing the average braking distances for each height that I measured. As you can see the results definitely show a strong positive correlation between the height of the ramp and the braking distance of the trolley.
(3) Skill Area A: Analysing Evidence and Drawing Conclusions
Analysis of Results:
My experiment shows that my prediction was right. My results show that as the height of the ramp increases the braking distance also increases. From my graph I can see that the height of the ramp and the braking distance are directly proportional in a way. This is because as the heights go up on the graph so does the braking distance therefore proving my prediction. However the graph shows that there were limitations with our apparatus and range as the graph does not show a complete straight line.
The Graph
I have chosen to represent my results in the form of a line graph, using a line of best fit. This shows the data best, and can be compared well to my prediction. The graph shows an approximate straight line. The results fit with theory and show that the distance of the trolley up the ramp is proportional to the stopping distance. This can be seen in the graph, which show a rough straight line, meaning the variables are proportional. As they are proportional it’s possible to estimate the braking distance of the trolley if the height is known. I can conclude, from my results, that my prediction was correct, and the distance of trolley up the ramp is proportional to the stopping distance. The science of this was explained in the earlier part of the coursework.
Graph:
Analysis of Graph
My graph proves that as the height increases the braking distance also increases and vice versa, this shows that my hypothesis was correct. With the graph the line of best fit obviously shows a very strong positive correlation between speed and braking distance, even when just looking at the results table it's plain to see. The slight curve suggests that another force is acting on the trolley and not allowing it to gradually increase braking distance. My results display that the higher the ramp the larger the braking distance. This is because an object, which is a certain distance above the ground, has gravitational potential energy (GPE), and when the trolley rolls down the ramp this energy is converted gradually into Kinetic Energy (KE). By the time the trolley reaches the end of the ramp all the GPE will have converted to KE.
Conclusion
The graph clearly shows there is a strong positive correlation between the height of the ramp and the stopping distance of the trolley. This is because the potential energy of the trolley when raised is converted into the kinetic energy of the trolley as it goes down the slope. As the height of the ramp affects the potential energy of the trolley it must affect the kinetic energy of the trolley as it goes down the slope. Both potential energy (mgh) and kinetic energy (½mv2) are affected by height of the trolley, if it is increased then so are the potential energy and the kinetic energy. This means that if the kinetic energy is greater, then an equal breaking force being applied in each case will take a longer distance to stop the motion of the trolley as the height of the trolley is increased. As the kinetic energy is affected by the height of the ramp this means that the height is directly proportional to the stopping distance as clearly shown in the graph.
This was the theory on which I based my prediction and it is clearly matched here in the results, as the correlation is strong.
(4) Skill Area E: Evaluating Evidence
I think that this experiment has gone very well for me. My results were of a particularly accurate standard. This is because I recorded three readings for each experiment and calculated an average from these times. They proved to be accurate as my repeat readings were very close to each other. The results also undoubtedly showed a relationship between the increase in ramp and the increase in braking distance of the trolley. There were no strange results (anomalies) within my results table and I think that this was because of the extreme caution and care that I put into making sure that the experiment was set up correctly with careful measuring.
The procedure and the manner of which the experiment was taken went smoothly with a few anomalous results. However I feel that the results were not very reliable as there were a few problems with the experiment procedure. Firstly, we used a toy car as the car went down the ramp it swerved in different directions, which may have made the results misleading. We changed soon afterwards and I therefore strongly recommend that a trolley should be used instead of a toy car. With this in mind, the results proved the prediction right, therefore showing that as the height of the ramp increases, so does the braking distance. Also one could measure the length of the ramp, and use a timer and measure the time taken for the car or trolley to stop after release from the top of the ramp.
I think that the method used in this experiment was a good way carrying out the investigation because it enabled us to gain results over a range of heights for the ramps. This combined with the repetition of the experiments meant that we had a wide range of data enabling us to find any anomalous results and find a clear correlation.
I believe that the experiment went very well because I did not face any major difficulties in obtaining or recording my results. If I had more time I would record more results to make my results more accurate. Using scientific instruments I could have measured the braking distance more accurately. Taking 3 sets of results reduced the chance of anomalous results. I believe my results were accurate as they were all near enough the same. Perhaps if I did the investigation again I would also see if mass affects braking distance.
Accuracy of Results
The results were measured very carefully and to the best of human judgement. I would estimate the results were measured to within the nearest centimetre. This is easily accurate enough to show a clear distance between heights, accurate enough that the repeated results didn't differ so much as a consequence of this correlation it proved my theory.
Also, the graphs are fairly accurate due to the precision of the results, and you can see that there is a fairly accurate straight line. All in all, I am satisfied with the reliability of the results, as they have enabled me to analyse and do what I need with them. However, as with any experiment there are the occasional anomalous results, which I got, but this did not hinder any of my work, and can be explained.
Strong evidence:
My evidence was reliable and strong enough to support my conclusion, in graph this was clearly exploited.
What Improvements Would Be Made If Redone?
1. Reduce the friction of the system.
2. Make the trolley more aerodynamic.
3. Electronically measure the stopping point for more accuracy with results.
4. Do the experiment more times.
5. I could use a real car but that would be very expensive and it would take a long time to get a lot of results, also biased results may occur.
If we did any of these proposals I'm sure we would get a fairer test with more accurate results.
Anomalous results:
As far as I can tell, no anomalous results were present, (An anomalous result being a result that does not agree with the general trend of the other readings).
Overview
Overall, I think that the experiment was conducted systematically, and produced enough results with reasonable precision, which allowed me to show my prediction to be true. It correlated well with the theory and there were not too many unexpected results.