This is why if you were to try dropping a steel ball, and a feather at the same time, the steel ball would hit the ground much sooner. That's not because of the difference in weight, but because of the difference in surface area. The feather has a greater surface area, thus a much lower terminal velocity.
This is similar to the case of the parachute. The air resistance of the parachute will always be the same but the greater the weight the basket contains the faster the parachute will fall. The preceding paragraphs set out my reasons for prediction concerned with the first factor.
Reasons for prediction of the second factor are as of the following:-
1. Taking into consideration the object will be falling at a constant speed common sense tells me the higher an object is released from, the longer it takes to reach the ground.
The height of each test will be measured in metres and centimetres and the average speed of each test will be calculated by the following equation:-
Average speed = Distance
Time taken
The apparatus we will require during the experiment will be listed as the following :-
- 40cm × 40cm sheet of cellophane
- 35cm long piece of string × 4
- A camera film case
- 2p’s × 5
- Metre rules × 2
- Stopwatch accurate to 0.01s
- Sellotape
- Hole puncher
- Weighing scales
- A table
Diagram
Step-by-step Method
The parachute was constructed by hole punching each of the four corners and then sello-taping 1 string to each corner of the cellophane square. The basket was then looped through the strings at the bottom and the required amount of coins added depending on the scenario.
The factors we are going to change are weight of the parachute and height by which the parachute is dropped from. The factors that we are keeping the same shall be the surface area of the parachute and the length of each string (between the parachute and mass.) We will then continue by dropping the parachute from different heights standing on a table if required. Each height will be tested containing a different weight and vice versa. The following heights and weights will be tested :-
1m -
1coin, 2 coins, 3 coins, 4 coins, 5 coins
1.25m -
1coin, 2 coins, 3 coins, 4 coins, 5 coins
1.50m -
1coin, 2 coins, 3 coins, 4 coins, 5 coins
1.75m -
1coin, 2 coins, 3 coins, 4 coins, 5 coins
2m -
1coin, 2 coins, 3 coins, 4 coins, 5 coins
The height of each test will be measured in metres and centimetres and the average speed of each test will be calculated by the following equation:-
Average speed = Distance
Time taken
To make our results as accurate as possible we will repeat any ‘duff’ experiments. This will include any obstruction to the parachute on its descent, whether or not the parachute was released and the timer started at exactly the same time and stopped at the time when the parachute touched the ground and also if any malfunctions with the parachute or basket occurred during the descent.
To ensure that our results are reliable we will repeat each single test three time and find the average with the following equation.
Result 1 + result 2 + result 3 = x_
3
‘Preliminary work has been noted above’
To certify safety, precautions must be taken while standing on high objects such as tables or chairs and also you must make sure before releasing the parachute that it is not going to collide with anything else.
Obtaining Results
Analysis
Each one of the graphs above shows a similar pattern to the rest. As the number of coins is increased the parachute takes a smaller amount of time to reach the ground. The common pattern shown on each graph is that of a curve going from high (left) to low (right).
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I can now make a conclusion in accordance to the graphs that as the weight contained inside the basket is increased the time it takes for the parachute as a whole to reach the ground in seconds in shorter. It can also be proved from the graphs that as you increase the height from which the parachute is being dropped it takes longer for it to reach the ground. This is shown by the higher starting and finishing point on each of the graphs as the height is increased.
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The reason why the parachute operated in this way is because the extra weight added to the basket acts as an extra force against gravity and air resistance therefore increasing the terminal velocity of the parachute. This explains why the parachute travels faster if it contains a heavier load. The explanation for the parachute taking longer to reach the ground is simply because there is a further distance to fall and so the time it takes is increased.
This is a constant variable because as long as the distance between the parachute and the ground keep on increasing the time taken to fall will be longer. The relation between weight of the parachute and time is also a constant variable: If the weight keeps on getting heavier the parachute will fall to the ground faster.
The conclusion I made supports my prediction in the fullest. All aspects of my prediction are repeated in the results of the experiment. I predicted that a larger amount of weight will cause the parachute to fall faster and the higher the parachute is dropped from, the longer the time until impact. Both of these predictions were proved to be correct when the experiment was done.
Evaluation
The best and most enjoyable part of the investigation was carrying out the experiments. To keep errors to a minimum we made sure that any anomalous results were repeated e.g. if the parachute hit an obstacle on the way done or paused or sped up for any reason the test was done again. We did obtain some ‘dud’ results throughout the experiment. These were usually caused by the parachute hitting a chair on the way down due to the unpredictability of the parachute concerned with where it was going on its descent.
I would say the reliability of our results was good and that to make the results more reliable the parachute would have to be constructed in a more methodical manner. To minimise direction changes the weight distribution would have to be perfect throughout and the attachments symmetrical all the way around.
The suitability of the procedure for the investigation was quite good although it could be improved by formulating some way of enabling the parachute to be dropped and the timer started at the same time to ensure fairness. This is the same for when the parachute touches the ground.
Providing additional relevant evidence to back up my conclusion could be done in a number of ways :-
- Further variables could be tested in order to find out more about the physics of the parachute e.g. (a) the surface area of the parachute, (b) the length of each string (between the parachute and mass), which might control the volume of air under the parachute, (c) the distribution of mass, i.e. perhaps on the parachute itself as opposed to on strings attached to the parachute.
- More tests could have been done to widen the range of evidence or to provide more evidence of what has already been done.
