Fair Test
To make sure that this experiment is a fair one, I shall be making all but one of the variable constant.
- The shape of the object – Keeping it cubed-shaped throughout.
- The surface area of the parachute – Keeping the parachute 50x50cm
- The length of the string between the parachute and the object – Keeping the string length 30cm
- The distance between where the parachute falls – Keeping it 2.65 meters
The only variable I am going to change is the mass of the object which is carried by the parachute. I am going to increase the mass by 1g each time.
Prediction
I predict that the terminal velocity of the parachute is reached later as the heavier the object, the longer it takes for the parachute to accelerate before reaching terminal velocity. Therefore, the larger the mass, the faster it will take for the parachute to land.
Apparatus
- Sticky tape
- String
- Plastacine
- Plastic sheet
- Ruler
- Measuring tape
- Stopwatch
- Scissors
Method
- Use the plastic sheet and cut out a square that is 50x50cm.
- Make a small hole at each corner of the square
- Cut 4, 30cm strings
- Put one string through each hole in the square and tie a knot so that the string will not come off the plastic sheet.
- Take plasticine and use a weighing scale and weigh out 5g, 6g, 7g, and 8g of plasticine, correct to 1mg.
- Stick the plasticine weight onto the four strings and mould it into a cube.
- Release the parachute at 2.65m and at the same time; take the time it takes to reach the floor.
- Record the results on a table
- Do steps 6-8 two more times and get the average.
Trial investigation
To make sure that my parachute would be able to work for the real test, I did a few quick tries to see if it worked. These are my readings:
Evaluation for Trial Investigation
This trial investigation has shown me that there are problems with my experiment. Firstly, the difference of 1g in mass does not affect the velocity greatly, and I have decided to increase the mass in 5g each. I have also decided to do 8 different masses. And instead of weighing 8 different weights, I shall weigh eight 5g plasticine and simply add on to the weights after each mass range.
Another I am going to change is the number of attempts I am going to do. I am going to do my experiment 3 times instead of 2 as it would be easier to find any significant/outstanding errors in the results.
The shape of my object, a cube shape is not ideal as moulding one is hard and can be inaccurate. I have decided to mould the objects into ball-shaped ones.
To make it easier for me to calculate the velocity of the parachute, I have chosen to change the height at which the parachute is released to 2m.
The holes in my parachute tore after a few tries as it were not reinforced, and the weight was tugging on it. To correct this problem, I made a new parachute and reinforced the holes by putting tape on both ends.
I did another trial with all my improvements and everything worked well, so I did not need to improve it any further.
Final Method
- Use the plastic sheet and cut out a square that is 50x50cm.
- Make a small hole at each corner of the square
- Cut 4, 30cm strings
- Put one string through each hole in the square and tie a knot so that the string will not come off the plastic sheet, and use tape to reinforce the holes.
- Take plasticine and use a weighing scale and weigh out eight, 5g of plasticine, correct to 1mg.
- Stick the plasticine weight onto the four strings and mould it into a ball.
- Release the parachute at 2m and at the same time; take the time it takes to reach the floor.
- Record the results on a table
- Do steps 6-8 two more times and get the average.
- Find the average velocity of each mass
Results
For some of my tries, there has been some reading that did not fit the pattern. I simply discarded those readings and did that particular try again.
To find out the average velocity of the parachute, we will have to use the following formula.
Velocity = Height / Time
Conclusion
I found out that as the mass of the parachute increases, the speed increases. Assuming that terminal velocity is reached, we can also say that as the mass of the parachute increases, the terminal velocity increases as well.
The graph, on the last page, has a line graph and a curve of best fit graph. Looking at the line graph, it can be seen that the graph levels off towards the last 2 or 3 masses. I will talk about that in my evaluation. The curve of best fit shows a positive correlation, and therefore shows that the mass of the parachute is directly proportional to its terminal velocity.
Evaluation
Overall, I think my experiment went pretty well. My results were pretty accurate to a certain extent. However, as I have said before in my conclusion, the last few results seemed to be the same. This could be due to the height of which my parachute was dropped. Since the height was quite low, some of the heavier parachutes might not have reached terminal velocity before landing, as the parachute with a larger mass needs to accelerate a greater distance before the opposing forces balance. Therefore, the parachute could’ve freefell to the ground before it reached terminal velocity.
There could also be some other errors in this experiment:
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The timing of the parachute could be inaccurate as the height of which the parachute was dropped may not have been high enough. Therefore, the parachute would be traveling so quickly that the stopwatch may not have been able to stop fast enough.
- I did this experiment in a corridor, which was slightly windy, and the parachute could have dropped to the ground diagonally, and not 2 metres straight down.
I think this experiment was fairly accurate, as it fits my prediction. However, it could have been improved more if:
- The parachute was dropped at a greater distance
- This experiment took place in a windless environment, such as the gymnasium
- Use a computer to time how long it the parachute takes to land
There were enough readings for me to make a firm conclusion and my readings were fairly accurate. However, it could be made sure to be more accurate with more results and at a greater height.
To improve my experiment, I would like to try investigating how the surface area of the parachute would affect the terminal velocity of the parachute. I predict that as the surface area increases, the time it would take for the parachute to reach the ground would also increase. This would happen as it will have more air resistance and it would collide with more air particles, and therefore take a longer time to reach terminal velocity.