An Investigation To Find Out What Effect The Weight Of A Falling Object Has On The Terminal Velocity Of It.

I am glad that I did a preliminary experiment, as now, when I do my actual experiment I will feel more confident using the apparatus.  I will also make sure that I am more accurate with the timing of the stopwatch, and change the dropping height so that it will be more accurate.

METHOD:

Diagram:

Method:

1.  Get the equipment set out correctly; (look at the diagram).
2.  Carefully get up on to the desktop.
3.  Hold the paper cutlet one metre above the metre ruler.  This is because terminal velocity is reached after a little while, not immediately after it has began to fall. By dropping it from one meter above the height from which it will be timed, it will have reached terminal velocity by then.
4.  Drop the paper cutlet.
5.  When the paper cutlet passes the metre ruler, simultaneously start the                  stopwatch.
6.  As soon as the paper cutlet hits the floor, stop the stopwatch.
7.  Record the time down on a table.
8.  Repeat the experiment for each weight three times.

Apparatus:

Safety precautions:

Through out my experiment, I want to make sure that I keep safety as one of my top priorities.  To do this I must make sure that:

1. Before standing on the desktops, I must make sure that there are no small    spillages of water or any liquids that I could slip on.

2. When standing on the desks to drop the paper cutlets, I am wearing trainers with a grip on the bottom of them, so that I do not fall off.
3. I must make sure that I exert extreem caution when getting up and down from the desk, so that I do not hurt myself.
4. I must remain aware of other people standing on top of the desktops, and make sure to be careful around them.
5. To ensure that no one else slips over, I must make sure to pick up any paper cutlets of the floor.

Fair Test:

To ensure that the experiment remains fair, there are certain variables that need to be controlled:

1. Make sure that you use the same equipment on every repeat of the      

experiment.

2. Let the same person start and stop the stopwatch, as some people have better eyesight and reaction times to others.
3. Use the same paper cutlet on every repeat of the experiment, as some weigh slightly different amounts to others.
4. Try to make sure that the paper cutlet does not change its surface area and become more spread out or more squashed together during the experiment.
5. Make sure that each repeat is dropped from the same height.
6. Make sure that there are no open windows or breezes any where near the experiment.

Reliable Results:

To ensure that my results are as reliable as possible, I will repeat the timing for each weight three times.  I will then calculate an average speed.  I will do this so that my results are more reliable and also so that it will be clear to see if I have any results that do not fit in.

CONCLUSION:

From looking at my graph and results, it is clear to see that as the weight of the falling object increases, so does the terminal velocity. I think that this is because the kinetic energy (                ) of the falling object, will be much greater for a heavier weight, than a lighter weight, as half of the mass is multiplied by the velocity squared.  This means that when the mass is transferred to kinetic energy, the difference between the masses will be increased even more and will result in faster kinetic energy. It is not just the difference in weights that will effect the speed of the falling objects, it is half the difference in mass multiplied by the velocity squared, which will make the original difference between the weights increase by a considerable amount when the difference is transferred into kinetic energy.

EVALUATION:

 

The results that I obtained fitted my prediction that as the mass of the falling object increased, so would the terminal velocity. Unfortunately, I was not able to find out if the second part of my prediction was correct, “I also predict that the lighter the paper case, the quicker it will reach its terminal velocity.  This is because to reach terminal velocity, the air resistance has to be equal to the accelerating force, if the accelerating force is less, then it should take less time for the air resistance to become equal to it.”  I was not able to find this out as I dropped all of the weights from the same height, and was not able to tell at which point they had reached terminal velocity.  If I was to do this investigation again, I would like to change it slightly, to try and find out if this part of my prediction was correct or not.

I could have increased the accuracy levels of my experiment by shutting a window that was near by.  I only realised that it was open when I had finished collecting my results.  This open window may have been the cause for the bigger range in my results for 0.7g, as it would have only really effected the lighter weights.  If I repeat this experiment, I will be certain to make sure that all surrounding windows are closed.  I would also try to do this experiment in a room with no other people in it.  This is because whilst conducting the experiment, people were walking passed, this created a breeze, and might have effected the speeds of the lighter weights.  I also noticed that as I got to the end of my experiment, the paper cutlet seemed to have spread out a little.  This meant that it’s surface area had increased slightly, making the test slightly unfair, as surface area is one of the factors that effect the speed.  Unfortunately there was nothing that I could do about this, as I could not change the paper cutlet, as they do not all weigh exactly the same amount.  

Overall, I think that my experiment went quite well. I feel that my results were almost as accurate as they could have been allowing for human error, as the ranges between them were low.  I did not have any anomalies that stood out after I re-did my set of results for 0.7gramms, this also shows that my results were quite reliable.  

I really enjoyed doing this experiment, if I had more time, I would extend it further to try and find out the other part of my prediction.  I would use computers to time when the paper cutlets reached terminal velocity.  This would be more accurate, as it would cut out the human error margin.  I would also try and find another object (whose surface area did not change) to test the terminal velocity of as the paper cutlets, surface area was easily changed, which made the test slightly unfair.