Safety
The only danger for this experiment is standing on the benches to hold up the rulers and drop the cone. To make this relatively safe, the bench must be stable. The only other possible safety point is to be careful not to get a paper cut (if somehow you do, wash under a tap).
Fair Testing
To make sure my experiment is fair, I will need to control as many other variable as possible. These variables are;
- Wind
- Drop height
- Method of drop
- Card cone
- Same equipment
Wind is a key variable that must be kept to minimum. If there is a significant draft or wind, the card cone may be blown off course (on course being straight downwards) or flips over and completely affect how fast the cone falls. To make sure this doesn’t happen during the experiment will be done indoors and I will do the experiment away from any drafts.
The drop height must stay the same otherwise there would be no point in doing the experiment. This is because if the height changed I would be doing more than one experiment. The only time I may change the drop height is during my preliminary experiments.
The drop method may be a less obvious variable, but it can make a difference. If dropped by hand it could be helped to fall. Also if dropped by hand it may not be dropped from the exact same height each time. To make sure the experiment is fair, I will make sure that I drop the cone the same way each time.
Each time the cone is dropped it must be in relatively the same condition. If the cone’s shape is changed a significant amount the speed it falls at may change, or if the card is ripped it will fall differently.
The measuring equipment should be the same for each drop because some equipment can give slightly different measurements. So I will use the same rulers and stopwatch.
Method
(diagram)
- Collect apparatus as shown in the above diagram.
- One person needs to drop the cone, the other time the drop.
- Drop the card cone from the top of the two metre rules, whilst timing the drop.
- Try to start timing as soon as the card cone is dropped and stop it as soon as the cone hits the floor.
- Repeat 3 times for each surface area to get more reliable results.
Prediction
I predict that the larger the surface area the faster the cone will reach its terminal velocity. If there is a small surface area, the cone will fall faster, reaching its terminal velocity slower. This is because there is less air resistance compared to gravity due to the small surface area.
Obtaining- preliminary experiment
These are my preliminary experiment results from a drop height of two metres.
I found out that the best drop height was two metres because we got the best results with this height. I also found out that the larger angles do not have definite results, therefore I will not go above 140o. This is because above this angle the amount of air resistance stays approximately the same.
Obtaining- final experiment
Conclusion
My graph shows that my prediction was correct. The larger the surface area the slower it travels and the faster the cone reaches its terminal velocity. My graph does, however show an anomalous result. The time for 253cm2 surface area is too slow to fit the line of best fit. This may be because one of the variables we were trying to control was not the same as it was when we did the other five surface areas. The cone may have flapped on the 253cm2 drop on the second attempt, causing the average for the three attempts to be higher. I would of liked to have taken the investigation further by investigating how weight affects terminal velocity so that I could be sure how these two variables affect terminal velocity together.
Evaluation
I think my results were reasonably reliable. There were some variables that I would have liked to have controlled a bit better, such as the drop height and drop method. The drop height was not exactly the same each time as it was hard to keep the rulers pointing straight up, one on top of the other. Also I would ideally have liked a mechanical drop method, which released the cone from exactly the same height each time and did not help the cone to fall in any way. Our experiment may not have been fair in that respect because we took terns in dropping the cone, therefore each having our own ‘precise’ way of dropping it. The same goes for our timing. We each took terns timing and everyone’s reaction times are different and it is therefore difficult to time the drop exactly as it is.
