I chose these heights, as I thought they where appropriate for the experiment we did. I chose them not be the same range from each height to the next to make it a clear comparison between them all.
- Put out the newspaper next to the sand tray, and light the candle.
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Hold the candle above the crater; tilt it slightly so the wax dips into the crater that was created. Let the wax dip into the 3 craters you made, making sure that it fills up to the full level, but don’t go over the top, wait until they have set properly, and lift it out of the sand and onto the newspapers.
- Then record your results like I have done of the graph paper.
- Do the same experiment, on the same heights but do each height 5 times, and record the results.
Calculation: GPE = m.h.g. = KE = 1/2mv2
Therefore v = √ (2.h.g)
Results Table
DATA ANAYLIS – graphs. *
The first graph I did was on my first set of results, which I test each height 3 times, the graph showed the relationship between the depth of crater to the height it was dropped.
- On my results table (depth of crater, height dropped from) which is on the back of the first graph, I circled two of my results which I feel are outliers, as they were way out of the other results that I had recorded.
- I think the outliers were caused by either the person dropping the ball bearing applied some pressure, or it wasn’t dropped at the exact height, or the sand was unlevel. We didn’t include most of the outliers which I thought were extravagantly different to my other results, so it wouldn’t affect my overall results that much. I also didn’t include the extravagant outliers on my averages; otherwise i would get an invalided set of data.
- I think most my results on my first experiment were reliable, but to make it fairer dropping the ball at more than 3 times, it would have made it even more reliable, than it already was.
Graph #2 –
My second graph showed the same as the first (showed the relationship between the height of depth of crater to the height it was dropped) but with an improved method.
- My second sets of results, in my opinion were a lot more reliable, as I tested it 5 times for each height, instead of 3 like the last time.
- Therefore I didn’t find any outlier, meaning my results were very reliable, because we made sure we did the second set of results more accurately and took more time. Meaning reliable results.
Graph #3 –
This graph show the relationship between the crater depths and velocity,
- I used the averages from my second sets of results as they were more accurate, meaning this graph would be more accurate.
Graph #4 -
This graph showed the relationship between the velocity and the height the ball bearing was dropped at.
- This graph is very accurate, it goes up at a steady pace, and the distances between each reading are very similar.
Improvements to the method –
I think my method was very good, but we didn’t do a few things that we probably should of, like:
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Every time you took the wax out of the crater, you should smooth down the sand, so lumps and bumps are at a minimum, making your results a lot more reliable.
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Made sure the magnet that was attached to the nail which held the ball bearing was exactly at the right height.
Explanations;
GPE (gravitational potential energy) - when you lift up an object you transfer the energy, this transfers into gravitational potential energy.
= mass x gravity x height
KE (kinetic energy) – is energy of motion. In this case before you drop the ball bearing it has GPE which is transferred into KE when you realise it.
= ½ x mass x velocity²
The conservation of energy - energy can not be destroyed or created.
How could I improve my results?
- In my opinion the test that I did was a far test, but you can’t be 100%, as someone could of added a little pressure when the ball bearing was dropped, that is properly what happened when we found outliers.
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Another possibility for our outliers is, when filling up the crater you need to make sure it does not spill over the edges, and that you don’t under fill it, it has to be actually level to be a fair test, and maybe in a few of ours they spilt over a little.
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You also have to be very careful that you are dropping it that the height you wanted, not a little bit over or under, otherwise that could change your results dramatically. You could maybe use another type of clamp to drop the ball meaning you wouldn’t be adding pressure, and you would be dropping it from the correct height like this:
- This would probably only work if you opened the knob quick enough otherwise it might affect the pressure of the ball bearing being dropped.
On my two results graph, some of my range bars overlap. This was probably caused by some outliers, that were not taken out, or at the time were not considered outliers. But now looking at it, they do look like outliers, meaning some of the range bars overlap.
To avoid this from happening you could make sure that when you drop the ball bearing you apply no pressure, and drop the ball at the exact height you require, as then it will minimise outliers, making your results a lot more reliable.
Conclusion;
- I think my results are quiet accurate, although I don’t think they are 100%, as a number of things could have happened, like what I mentioned above.
- On my first set of results, I found two outliers, i thought they were both outliers because they were 0.4 below the lowest of the other results, this is probably because when it was dropped it was dropped slightly lower than they should have.
Most of my results don’t have a large range making them more accurate the biggest range I have is (without outliers) 0.3cm so a close range.
I think reasons why they could have been inaccurate, are that the heights which they were dropped were not precise enough, and people many putting a little pressure on the ball bearing causing inaccurate results.
- If I had more time I would have made sure everything was done very carefully and accurately, and there are a couple of outliers which if i had time would have tested them again.
- I am fairly confident with my results, but like I have said I would have like to re-do some of the outliers I found.
I think my experiment was quiet successful, apart from the few outliers, which was probably due to pressure of dropping the ball bearings or it was not dropped at the correct height.
