Preliminary Work:
To aid our experiment, we have undertaken a series of preliminary steps. Firstly we chose the maximum and minimum heights of our ramp. If the ramp was too high, the trolley would hit the floor too hard, resulting on a drop in speed. If the ramp was too low, the trolley would not move. We also chose a mid height and 2 heights in between our extremes. We then performed the experiment on these heights to see if they were indeed suitable for the experiment. These were our results:
Max: 87.7cm = 0.74secs
Quarter 1: 75cm = 0.84secs
Mid height: 60cm = 0.87secs
Quarter 2: 45cm =1.05secs
Min: 29.8cm = 1.29secs
We chose to time the trolley over a distance of 2m from when it leaves the ramp. We chose this because any smaller distance would be very difficult to time, as the trolley would be travelling too fast to get a real result and any larger distance would not be suitable for our safety regulations. Looking at the results, it seems that so far my prediction has been right – the higher the ramp, the faster the trolley travels. I am going to keep these results as they will make good points to compare my final result to. We will perform each part of the experiment 3 times to get an average result to plot onto a graph.
Method:
Take the ramp and set it up at the first height chosen.
Place the trolley on the top pf the ramp.
Mark the floor with some string or the metre ruler at your chosen distance.
Let the trolley go, without applying and force to it. Simply let it roll down the ramp itself.
Start the stopwatch as soon as the trolley leaves the ramp.
Stop the stopwatch as soon as the trolley reaches the set distance.
Record your result
Repeat with the other chosen heights.
Fair Test:
To ensure that our experiment goes well and that our results are fair, we will use exactly the same trolley for each part of the experiment. If possible, we will perform our experiment in the same place around the room on each day of the experiment. We will also be as accurate as possible with all measurements and times to get the best results. Our equipment will help with this, as they are very reliable sources. Probably the most important element of fair test in this experiment is the distance we use. Each time, we will make sure that the ramp is the same length and the distance between starting and stopping the stopwatch is also the same.
Results: All heights are written in centimetres. All times are measured in seconds.
I am very pleased with our results.
Conclusion:
As you can see from the table and the graph (Over page), as we decreased the height of the ramp, the time it took for the trolley to complete the 2 metres increased. I believe that this is, as said in the Prediction, due to the rule of as you increase the Gravitational Potential Energy, the amount of Kinetic energy will increase, thus meaning an increase in Velocity. (K.E=1/2 x Mass x Velocity x Velocity.) With more speed and more Kinetic energy, the trolley could get from the bottom of the ramp to the end of the course in a shorter time.
Therefore, this matches what I predicted before the experiment took place. My results turned out exactly the way that I thought they would. I am very pleased with the results that I obtained from this experiment. The only result that seems to stand out a little is attempt 3 from our largest height – 0.79secs. This is, as you can see by referring to the table, quite a lot faster than the other results taken from this height. We decided to keep this result in rather than redo that part of the experiment as it would make an interesting observation. Comparing the final results to the preliminary results, it seems that our final pattern also fits with our preliminary results. We have completed the preliminary experiments to give us an aid with the secondary stages of the investigation. It was very important to have our preliminary results as we needed to test our experiment for affectability
Evaluation:
I am very pleased with the way our experiment went. We completed our task without any accidents and all of our equipment worked well. I think that the way we timed the trolley from the start to the end of the course was quite efficient and gave us quite reliable results. However, if we wanted to improve our timing method, we could have used a Motion Gate. We would have placed one end at the bottom of the ramp so that the clock would be started at the exact moment the trolley went past. The other end would need to be placed at the 2 metre mark so that the clock could be stopped at the exact moment the trolley finished the course. This method of timing would have made excellently accurate results that could be reliable to be correct every time. As said in my conclusion, we found 1 result that stood out. Attempt 3 on our highest height. I don’t know exactly why this result was so much smaller than our other results. However, as this was our only result that looked different, we left it in our experiment. We had enough information to draw a conclusion and as our results fit in with our prediction I feel that my conclusion is accurate. If I was to re-write my method, I would have liked to use the motion gates instead of the stopwatch to obtain more accuracy ob my results and I would have also liked to have used a lighter trolley aswell so that we could compare our results and see if mass had anything to do with the result. I am glad that we took our preliminary results when we did as it was this that gave us reasonable heights to begin the experiment with.