Friction – if there is more friction on the surface of the runway and ramp, the trolley will not be able to pick up much speed and also be aided to stop by the friction. And if the surface has too little or no friction at all then the trolley will pick up too much speed and it would be very hard to stop it. Therefore the surface of the ramp and the runway must not have too much nor too little friction, but still it should be more towards little than big. For this reason the same surfaced runway and ramp will be used.
Apparatus:
- Trolley
- Ramp
- Runway
- 1m ruler
- Stool
- Masses
- Pulleys
- String
- Marker pen
If the apparatus were set up like this then it would be very easy to measure the distances. The trolley will be released from the top of the ramp. When it stops and starts to come back on the runway, the runway will be marked at where the trolley was stationary. The same mass of the trolley will be measured twice and then if the results are far apart then a third will be taken to determine an average. After the same mass of the trolley has been measured twice or three times then more masses will be added to the trolley and then the same will be repeated.
As we need an average of the different results there will be no point in re-doing anything because we already have an accurate result.
Safety – there is one safety precaution to be taken seriously. This is the mass; one must make sure that they do not fall on their hands, feet etc.
Preliminary experiment
Diagram
Method
The experiment was set up as shown in the diagram above. A braking force (mass hung from the end of the stool) was added. The trolley was then released and the stopping distance was recorded. The messes of the trolley were changed to see if the effect of the braking force good enough to stop the heavier trolley, but also not to strong that the lighter massed trolley would fly back without covering much distance.
Results
Conclusion
From this experiment we have gathered that the perfect braking force will have to be 500g. This is because the braking force of 1kg was blatantly too big because the trolley instantly flipped backwards. 700g was also too big for the trolley to be stopped with a fair deal of distance. 300g was too small a force for the mass when extra mass was added. 500g was ideal as it worked for the smallest mass of the trolley and also the largest.
Obtaining Evidence
There were no additional changes made to the planned method. The same idea was used but I started of with the measuring of the length of the ramp and also the height and angle of it. The length of the ramp was approximately 80cm and the height was approximately 19cm. With this information the angle can also be measured, which was 13.7º.
The results were taken in the way mentioned in the planning. This is by taking two results and then if they are far apart take a third. Then if it is hard to determine the anomalous result then take an average of all three. But if it is easy to determine the anomalous then don’t add it in the average. For example with 4 weights there is no need to put all three in the average because 24cm is nowhere near 47cm and 48cm.
Analysing Evidence and Drawing Conclusions
We can tell from the results that the higher the mass of the trolley there will be the longer the stopping distance will be. This is because if something is moving and it is heavy then we know that it will take longer to stop than if the same object is moving and it is light. An example of this theory is that if a rhino is running at someone then it would collide with the person and injure him or her but if a cat is running at the same pace it would just collide with the person and just fall over most probably injuring itself. This is because of its mass.
As I thought before I carried the experiment out the more the mass of the trolley there would be the harder it would be to stop and therefore the stopping distance will be greater. This was my prediction and that is exactly what happened in the results. I think my prediction was accurate because it is obvious that a heavier object is harder to stop than a lighter object.
Evaluating Evidence
I think that most of my method for carrying out the experiment was a good way to do it because the results reflected what was expected by the scientific theories. I think that the way the trolley was released from the same place was good because everytime the trolley was released it was from the same place and therefore the results were made more accurate. I also thought that the position where the brakes were applied was also kept the same everytime by making sure the string, which was acting as the brakes, was always the same length. However I believe that if I were to do the experiment again I would try to use a different way to measure the stopping distances because our eyes are not too accurate to see the exact place where the trolley became stationary and started to go back. I know this because during the experiment I found that it was very hard to be accurate when marking the runway. I am sure that the results I gained however were easily reliable enough to make a conclusion from because they weren’t many anomalous results and the results showed why what was achieved.
