When a free-falling object first sets off it has much more force accelerating it than resistance slowing it down. As the speed increases the resistance builds up. This gradually reduces the acceleration until eventually the resistance force is equal to the accelerating force and then it won’t be able to accelerate anymore. It will have reached its maximum speed or Terminal velocity.
Preliminary Results
After the results that I got from my preliminary results I decided to change a few things in my original method. First of all I changed the height from which I am dropping the marble. The reason for this is that the best results came within 10-160cms. I also changed the amount of times I will do the experiment. I have decided to repeat it three times.
The change in heights I made to my method improved the results I got for my real practical. My results where much better than my preliminary results and I was able to produce a much better graph because of this. The change in the amount of times I was going to do my experiment improved my final results because it made them more accurate.
Results
Test 1
Test 2
Test 3
Below is a table showing the average radiuses and areas of the craters which were made in the sand. (Taken from all three experiments)
My results that I got form my experiments I found that my predictions were correct. The higher the height from which the marble was dropped the greater the area of the crater was. I also proved that once the marble was dropped from a certain height and above the area of the crater stayed the same. I proved this in my preliminary experiment.
I think that my experiment was fairly accurate but I don’t believe that it was completely accurate. This is because it is hard to drop the marble from the exact height from which it is supposed to drop. Also it was hard to measure accurately the area and the radius of each of the craters made. My experiment was repeatable but I believe that if everything was 100% accurate then the areas of the craters would be the same each repeat. I don’t believe that my results are completely reliable because I could have been a centimetre too high or too low when dropping the marble.
Graph calculations
Averages
Area for craters from 10cm-
Area for craters from 35cm-
Area for craters from 60cm
Area for craters from 85cm-
Area for craters from 100cm-
Area for craters from 110cm-
Graphs
I am happy with the graphs that I have produced. The graph I have drawn with my three different experiments on it shows correlation. All the lines are very steep and start getting less so as the ‘height from which the marble is dropped’ gets higher. All the lines follow the same trend. On my graph two of my lines intercept. This only happens because my results cannot be 100% accurate. If my results were completely accurate this would not happen. The graph I drew showing the averages of my three experiments came out very well. The curve is quite steep. The gradient of the curve changes constantly but causes the line to be steep.
Conclusion
From my results I have found some good trends. The higher the height from which a marble is dropped into sand the larger the area of the crater made is. I have also found from my preliminary results that at a certain height the area of the crater stays the same. Over all I think my investigation has gone well. My prediction saying that ‘the higher from which the marble was dropped the bigger the area of the crater would be’ was correct. My other prediction was also correct which said ‘after a certain height from which the marble was being dropped the area of the crater would stay the same’.
I had some anomalous data in my results. Technically all my results for each repeat should be the same but they were not. This is because it is impossible to be completely accurate whilst carrying out my experiments. I could improve my method by dropping the marble from 15 different heights instead of 6. This would give me better results. I am happy with the accuracy of my results and they did not vary more than I would like.
My prediction saying ‘the higher from which the marble was dropped the bigger the area of the crater would be’ was correct because when the marble is falling it builds up more speed due to acceleration. The more speed it builds up the more force is being used accelerating it which is then exerted on the sand. The more force exerted onto the sand the more sand it is able to push away therefore making a bigger crater. My other prediction saying ‘after a certain height from which the marble was being dropped the area of the crater would stay the same’ was correct because when a free-falling object first sets off it has much more force accelerating it than resistance slowing it down. As the speed increases the resistance builds up. This gradually reduces the acceleration until eventually the resistance force is equal to the accelerating force and then it won’t be able to accelerate anymore. This means it will have reached its terminal velocity and wont go any faster. This means that the crater will stay the same from a certain height and above.
BIBLIOGRAPHY
The Science Coordination Group – Revision Guide for GCSE Double Science, Physics Higher Level.
