Length: 1119 words (3.2 double-spaced pages)
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The aim of this investigation is to find out how one chosen variable
can affect the rate of descent of a parachute. There are many
different factors that can be taken into consideration and varied to
see what has the best effects on the rate of descent. The options
a) The size of the canopy,
b) The weight pulling on the parachute,
c) The length of the chords,
d) The shape of the canopy
Also the forces acting on the parachute had to be taken into
consideration and appreciated for how they could be influenced or used
to aid the rate of descent.
The forces came in the form of air resistance and gravity.
I chose to see what the effects of the weight the parachute had to
support would have on the rate of its descent. My original prediction
after some general thinking was that the heavier the parachute was,
the faster the parachute would descend. I believe this to be totally
true as it is a logical thought process; a feather falls slower than a
hammer indicating heavier objects fall quicker than lighter objects.
Also the aerodynamics matters, if a surface area of a side of a brick
is cut out on a piece of paper and dropped at the same time as the
brick the brick will hit the ground before the paper. This is because
heavier objects fall to the ground quicker than lighter ones.
The next question is why is this important? It matters because if
something is falling to fast or slow then other variables can be
changed to counter act this, e.g. the size of the canopy or the
aerodynamics of the weight. The object that needs to be controlled is
air resistance; this is made higher or lower by parts of the
parachute. The more air resistance created by the canopy then the
slower the parachute will fall. What also matters is how the weight is
distributed from the parachute.
If the ballast pulls in the canopy
then the canopy will catch less air and make less air resistance
making the parachute fall faster and may cause damage to person using
the parachute which could be catastrophic.
To prevent this modern parachutes are very advanced, they include
parts to make the canopy stay fully opened and other features to make
it fall straight and not move where the air takes. Unfortunately only
so much technology can be used with a bin liner, cotton and plastocene
but I feel that the following method is suitable for the needs of the
The Method for making the Parachute
A parachute consists of three main parts, such as the canopy, the
ballast and the chords. I will explain the design of the parachute and
what has been done.
Firstly I made a circular canopy as I thought it would be the best
shape. What influenced my choice is that it was the nearest to the
shape of parachutes that real paratroopers use. I decided that if the
shape is good enough for paratroopers, it's good enough for me. The
only problem is that on a real life parachute, there are skirts around
the edges like on a Hovercraft to hold air in, and maximise air
resistance. Unfortunately this was to complex a design to make. The
radius of the parachute was 15cm thus giving it an overall area of
225cm2. This appeared a suitably large area for the experiment. The
only material available to make the canopy was a bin liner, or a
plastic bag as we now call it. This is a thin material but it was
suitable for the investigation.
I then used fairly thick cotton string to hold the weight onto the
parachute. The length of this string was 17cm. This was set as it was
as it looked in the right proportions to the parachute. There were no
real scientific ways of making the string the correct length in
proportion to the canopy.
Testing and Results
The next step was to test the parachute to make sure it fell to earth
in a moderately steady fashion and gain some results to prove my
prediction and investigate parachutes.
The test drops were successful without any ballast and the parachute
fell to earth or the floor of the science room without drifting very
far away from the point of release. One obvious thing that could be
observed is that the parachute fell in a spiral indicating that the
weight already was not distributed evenly over the four connecting
points of the cord to the canopy, or there was a an air current in the
science room. This could not be made perfect and the balance was only
slightly out and so I left this, as I did not consider this to make
much difference to the descent of the parachute.
After the parachute was tested an official plan was laid out. The
parachute would be dropped from two meters. This was decided, as it
would be a better scale to be plotted on a graph and was a safe height
to be dropped from, as there was not much stability in standing on
tables in the science room.
I decided that the parachute should be dropped with each weight three
times to gain an average as the results would then be more reliable
than one off results. After three drops of the parachute 5 grams of
plastocene would be added, as this was a large weight in terms of the
parachute size to be added. The final weight that the parachute would
end up carrying would be 30 grams.
Parachute + 5g
Parachute + 10g
Parachute + 15g
Parachute + 20g
Parachute + 25g
Parachute + 30g
Analysis of Results
The results in the table in the previous page are all different and
show a slight pattern but when it is in a graph (graph on next page) a
clear trends appears.
Sadly at the time of testing I did not consider dropping the parachute
without any ballast so I do not have any times for the parachute with
By using an average line on the graph the overall picture is revealed,
it shows all the research in one rather than looking at lots of lines.
On the average line with the least weight it is obviously going to
fall slower than the heavier weights and this was proven on the graph.
When the parachute had fifteen grams of ballast it fell very quickly
then it slowed down again. It got slower with twenty to twenty five
grams and then increased with thirty grams. The best weight for the
parachute to hold is either five grams or twenty-five grams.
Twenty-five grams is a more realistic weight for the parachute to
hold. From these results the weight of the parachute can be multiplied
to a man's weight and then the ratio can be used for the canopy and
cord to do the same. The weight can be then tested on a scale model.
With this data the parachute can be made to measure any person to
provide the ideal descent speed for that person and the safest landing
The results did not fully turn out how I expected them to. I expected
that as more and more weight was added the parachute would keep
falling at faster speeds. I don't think the results turned out as I
expected there must have been a mistake some were along the line when
the results were obtained. I think it was when they were recorded.
Overall the experiment was not a major success, as the results did not
seem correct. I do not think that the evidence is very reliable.
Looking at how I conducted the experiment I would like to repeat the
investigation and be more careful and precise when I obtain results. I
would take more care when I record the results and double check each
one to make sure that it is correct. The results as a whole were
There is enough evidence from the results to say that the lighter the
ballast on the parachute then the more assurance there is for a
smoother journey to ground. I think this would apply to all
If I ever repeat this investigation I will defiantly use more than one
parachute of the same size and repeat all the tests three times so I
gain the average results of three parachutes. With more results the
trend of the parachutes becomes more apparent and better points and
conclusion be drawn from them.
This investigation was not a success or failure but a stepping-stone
into how to plan and do a better investigation next time.