I think that the first movement of the tub (no mass) will go the furthest and the last one (500 grams) will move the shortest. The distance travelled will decrease steadily as we add the mass.
Apparatus List
- Stool (constant)
- Elastic Band (constant)
- Newton Meter (constant 15N)
- Chalk (constant)
- Margarine Tub (constant)
- 50g weights (variable)
- 3 Meter Sticks (constant)
Method
First of all I gathered the equipment I’d need to carry out the experiments and then I set them up (see apparatus list and diagram). I used a stretch of the sports link corridor because there’s plenty of space and the surface is relatively smooth (to reduce friction between the tub and floor).
I placed the stool in front of a stretch of the floor and attached the rubber band between the front two legs.
Placing two metre sticks in a straight line facing the stool, I got a person to sit on the stool to balance the force that would be exerted on it (so that the stool does not move).
With the Newton metre’s hook on the elastic band behind the tub, I pulled it back so that it read 15 Newton’s. I let go of the elastic band and the tub moved forward depending on how much mass was in it.
I marked on the ground by the ruler how far the tub moved and then recorded all the marks in a table.
After completing this, I performed the experiment again because I wanted to see if my results were conclusive enough. If there was any results that looked wrong or out of place then I would know that they were bad. There was a result that looked wrong (see results table on next page) so I repeated the experiment for the third time and the results were conclusive.
Analysis
Results
Results Of 1st Experiment Results Of 2nd Experiment Results Of 3rd Experiment
(See 1st graph) (See 2nd graph) (See 2nd graph)
Conclusion
The preliminary results
I think that my prediction corresponded with my results very well. The results show
that there is generally a steady decrease in the distance travelled as I added more
mass.
Graphs 1 and 3 show a smooth curve with no bad results, they show conclusive results
and the values are close together and the greatest difference between all 3 sets of
results is 8cm (1st graph 0 mass minus 2nd graph 0 mass).
There is a general trend in the results; from 0 mass to a 50g is where the greatest
distance difference occurs (1st graph = 295 minus 167 which equals a difference of
128cm), (2nd graph = 287 minus 172 which equals a difference of 115cm), (3rd graph
= 293 minus 169 which equals a difference of 124cm). So the average of the
difference between the first two values is 122cm.
As the mass increases, the distance between each individual value decreases. As you
can see on the graphs, at first the distance between the values is quite big (steeper)
then as the mass is increased, they become closer together.
I think that there is such a big difference between the first two values because the tub
itself will hardly weigh anything In comparison to the 50g weights so it will be able to
go much further with less force exerted on the ground and so less friction to slow it
down.
I found out that the average difference between the values of the first experiment was
28cm (rounded up to 1dp from 27.7cm). I then found out what they were for the
second and 3rd experiments: 2nd = 27cm (rounded down to 1dp from 27.1cm) and 3rd
experiment = 28cm (rounded up from 27.6cm).
The averages are all either 27 or 28, this shows that all three sets of results have
something in common and that they generally have the same results with no obtrusive
results.
Evaluation
All 3 experiments went very well, I performed them well and collected a good set of
data to aid me with my prediction.
I predicted that as I added more mass, the distance that the tub travelled would
decrease, through performing the experiments I found out that this was true. I think that to make the experiment better and make the results more reliable, I could have performed the same experiment more times (maybe 5 or 6) this would have given me a larger range of results and therefore a better view of the actual values and distances.
I could have also cleaned the floor before each experiment that I failed to do on all of them, this would mean that there would be the same amount of friction present at each experiment.
I think that my results were reliable to a certain extent. I don’t think that they were extremely accurate because some of the distances measured by the ruler were rounded off to the nearest centimetre so they would not have been perfect. Also, the force (15N) that was used to move the tub may have been slightly different each time it was used because there was two people doing it and they may have had different interpretations of where put move the marker (above or below the 15N line on the Newton meter).
Nearly all of my results were accurate except for 1 (2nd experiment on 200g) it was way below the result before (52g gap) and so it must have been wrong. I think this could have happened for various reasons; The elastic band may not have been touching the tub completely so not all of the force was put onto the tub, the Newton Meter may have not been put on 15N so the distance was lower than it should be, or the weight may not have been centred in the middle of the tub (the elastic band could have hit the weight and not the tub making some of the force be absorbed into the weight).
