Safety:
The experiment is not very dangerous however there is still the risk of a small electric shock as I will be using electricity. Therefore I will ensure that hands will not be wet whilst touching electrical components. Also the trolley going down the ramp will need to be stopped otherwise it will fall on the floor and possibly cause injury or damage to the apparatus. To stop this from happening, I will face the ramp towards the wall so that the trolley hits the wall at the end of the ramp and it stops moving. I will keep all leads out of the way so that it is not possible to trip over them and they do not twist or tear.
Fair Test:
To keep this experiment a fair test, I will only change one factor (the height of the ramp) and everything else will stay the same, things like the distances in between the two light gates, the mass of the trolley, and the surface of the actual ramp. To make sure there are no errors and no unfairness, I will check that the apparatus has been set up correctly before taking each set of results and I will check that the other factors have not been changed.
Prediction:
I predict that as the ramp gets higher it will take less time for the trolley to reach the bottom as the gradient becomes steeper and so it will take longer for the trolley to reach terminal velocity. I predict that as the height of the ramp is doubled, the time taken for the trolley to reach the bottom will divide by two. Therefore I predict there to be a strong negative correlation as shown in the graph.
I will also be calculating the average speed of the trolley. I predict that with a greater height, there will be a higher average speed. The reason for this is that speed is distance over time. If the distance stays the same but the time decreases (the height of the ramp is increased), the average speed will increase.
Speed = Distance
Time
Therefore the less time the trolley takes, the higher the speed will be. If the time is doubled, the speed will be halved.
Preliminary Work:
I will be carrying out a preliminary experiment so as I can gain a greater understanding into what the main investigation will be like. To do this preliminary I will be using the following apparatus.
- Q.E.D.
- Two light gates
- Linking leads
- Trolley
- Ramp
- Lab jack
- Metre rule
- Clamp stands and bosses
Method:
1. Set up the experiment as shown in the diagram.
2. Take three sets of results for each height to obtain an average and so that anomalies can be spotted easily.
Diagram:
Results:
Conclusion:
The results of the preliminary support my prediction as the graph shows that there is a strong negative correlation saying that as the height increases, the time decreases.
The second graph also strongly supports my prediction that with a higher ramp, the speed will be higher because less time will be required for the trolley to reach the bottom. There is a general curve showing that as the height of the ramp increases, so does the speed of the trolley.
Improvements/Changes:
I believe that the experiment has worked successfully and that no changes or improvements need to be made.
Further work:
In the main experiment I will be working out the average speeds to see whether the height of the ramp is directly proportional to the speed of the trolley. In order to work this out I will be dividing the distance by the time. The distance is always 70cm and the time will vary with different heights as seen in the graph. It will be measured in (cm/s).
Speed = Distance
Time
Observations:
Analysis:
The evidence in the observations shows a trend where increasing the height of the ramp, decreases the time taken for the trolley to reach the bottom. It also shows that with an increase of height, there is an increase of average speed at which the trolley travels.
Graph 1:
From the first graph, it is possible to conclude that as the height of the ramp increases, the time taken for the trolley to reach the bottom decreases. This strongly supports our predictions where the higher the ramp, the less time will be needed for the trolley. However it does not support the statement that doubling the height will half the time. This is because there is a steady decrease in time with a curve shown in the graph. This shows that the biggest decrease of time taken is at the beginning and the values become less spread apart making a curve. There is a trend because the line is showing a negative correlation. However there is no obvious pattern because the difference between each consecutive measurement decreases each time.
The Product Moment Correlation Coefficient between the height and time is -0.3. This is a weak negative correlation and means that with an increase in height, there is a weak direct decrease of time.
Graph 2:
From the second graph, I can see that with an increase of height there is a clear increase of speed. However, from the graph, I can conclude that doubling the height does not double the speed taken for the trolley to reach the bottom. The curve on the graph is very similar to the prediction graph. This suggests that my prediction has been supported very strongly. With a steeper slope, there is a much smaller time needed to travel 70cm down the slope and therefore:
Less time = Higher average speed
Speed = Distance
Time
If we input values for the distance and time and then decrease the value for time there will be an increase in the value for speed:
Distance = 4cm
Time = 2s
Distance = 4cm
Time = 1s
From this example, it is possible to conclude that if the time is halved, the average speed will be doubled.
The Product Moment Correlation Coefficient between height and speed is 0.9. This is very strong positive correlation meaning that with an increase of height, there is a direct increase in speed at almost the same rate.
Evaluation:
I believe that the procedure used was accurate and successful as we have performed our aim correctly. However there were a few anomalies which have been accounted for.
Anomalies:
These following results are anomalous because if a trend line were to be drawn in the graphs, they would not be exactly on the trend line like the rest of the points. However they are not very far off so on the whole the experiment can’t be said to be inaccurate in this way.
I feel that overall the results were quite accurate. This is can be seen when looking at the graphs, which show a straight line with all of the points apart from one or a few being very close to or on that line.
The reasons for these few inaccurate results may have been as followed:
- The trolley may have been pushed slightly at the beginning therefore giving it an advantage.
- The apparatus might not have been set up correctly meaning that results could have been abnormal.
- The height of the trolley might not have been measured correctly and therefore, with a greater height, the trolley would have gone faster with a lower time.
As there were only three anomalies, I can say that the results obtained are reliable to the extent that a clear conclusion can be made from them. I believe that the results obtained do strongly support my conclusion and that further results do not need to be taken apart from the three anomalies which should be repeated.
Further work:
In addition to the experiment, further work does not need to be done. However to obtain more evidence to support my predictions and possibly to make another prediction, I would also vary another variable. The variable I would choose to vary would add a weight to the trolley pulling it down the ramp. This would speed it up and I would vary the amount of weights. To obtain good results I would drop the weight down onto the floor from a string attached to the trolley with the help of a pulley. With more weights, I would predict that the trolley would go faster down the slope and therefore there would be a lower time.
