Method:
Experiment 1 – Different Shaped Parachutes
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first you need to get the same surface area for each of the three shapes, this is done by using the formulas, A=l2 for the square parachute, A=0.5*b8h for the triangular parachute and A=∏*r2 for the circular parachute
- Get one of the plastic bags and cut the bottom of it and down one of the sides so that it is now one sheet of plastic, also cut of the handles.
- Draw out a square with a length of 15.5cm on to the plastic and cut it out.
- Draw out a triangle with a two side lengths of 22cm and one side length of 31cm on to the plastic and cut it out.
- Draw out a circle using a compass on to the plastic with a radius of 8.78cm
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Each of these shapes has a surface area of 242cm2, test this with the formulas above.
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This on the corner of each shape mark in 1cm and cut a small whole to tie the string onto (for the circle work out the circumference using 2∏r and then divide it by six, so it is a piece of string every 9cm)
- Once you done this measure each piece of string to 30cm and cut it off, then group the string on each parachute and wrap a piece of sticky tape around the end.
- Now get a bit of glue tack and stick it on the end of the sting and then to the washer.
- Get a 2.5m ladder (use an A frame ladder for safety reasons) and place it next a wall
- Measure 3m up the wall and mark it, this will be the point where the parachutes will be dropped from.
- Now drop each parachute three times from this point by making sure the bottom on the washer is level with the mark on the wall.
- Time each drop using a stop watch and recorded results.
Experiment 2 – Different Surface Area
- Get the other plastic bag and cut the bottom of it and down one of the sides so that it is now one sheet of plastic, also cut of the handles. You may need to bags for this depending on your spacing between each.
- Draw out three circles using a compass, the first one having a radius of 5cm, the second one 10cm and the last one 15cm.
- Cut each of these circles out.
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Know work out the Circumference of each circle (2∏R) and the divide it by six, then
- Now make a small whole at each of these points and tie a piece of string on to each
- Measure each piece out to 30cm and cut of the end
- Group the ends of the string of each parachute together and wrap a piece of sticky tape around the end.
- Now get a bit of glue tack and stick it on the end of the sting and then to the washer.
- Now go back to the where you dropped your parachutes for the first half of this experiment, and drop this set. Again making sure that the washer is level with the point on the wall.
- Drop each parachute three times, timing each drop and recording your results.
Difficulties Overcome:
One of the major problems I had at the start of this investigation for Experiment 1 was to try and get every shape to have the same surface area. In the end I found it easiest to get the length and area of the triangle and the just manipulate the area formulas for the square and circle to make them both equal the triangle and then work out the length and radius accordingly.
Another problem I had was cutting the shapes out along the lines I had draw. Because the plastic keeps slipping in between the blades of the scissors and not cutting the plastic or it would cut of the lines. This was overcome by simply getting a sharper pair of scissors and stretch the plastic out as I cut it.
Results:
Experiment 1- Different Shaped Parachutes
Experiment 2 – Different Surface Area
Analysis:
Experiment 1
Surface area of each parachute.
Area of a triangle: A = 0.5*b*h
= 0.5*22*22
= 242cm2
Area of a Square: A = l2
242= l2
√242 = l
l = 15.56cm
Area of a circle: A = ∏r2
242 = ∏r2
242/∏ = r2
√77.03 = r
r = 8.78cm
Experiment 2
Total Surface Area
Parachute 1 A = ∏r2
= ∏*152
= 78,54cm2
Experiment 1 and 2
Placing of the Strings for the circular parachutes.
C = 2∏R
= 2*∏*8.78
= 55.17cm
= 55.17/6
= 9.1cm apart
Average time for each drop
Average = (1+2+3)/3
= (1.29 + 1.21 + 1.26)/3
= 1.253
Discussion:
In experiment 1, even though all the parachutes had the same surface area, not tall the shapes had the ability to catch the air and slow it down. The triangle and square aloud for the air to escape from the sides thus not reducing the speed of the decent. Where as the circular parachute made a canopy creating more drag as the parachute fell to the ground.
In experiment to it is obvious that the lager the surface area the slower the decent, if we look at the differences in time between the 5cm radius parachute and the 15 we can see that the larger the surface area more drag is created and thus its slows down the terminal velocity of the drop.
Conclusion:
I have proved that the lager the surface area of the parachute the slower the decent of the fall, this is caused because the parachute collides with more air particles on the way down slowing the decent. Also the shape of the parachute is very important, if the parachute dose not have the ability to create a large amount of drag then there is not going to be a major decrease in the rate of decent.
Evaluation:
If I was to do this test again, I would make all my parachutes have a larger surface area, because during the drops of parachute one in experiment 2, the parachute didn’t seem to affect the rate of decent at all. I would also drop the weight without any parachute attached so that i could really see the affects the parachute had on the rate of decent. Lastly I would try and relate the practical more to real life drops, by using comely used shapes of parachutes instead of just basic shapes.
Bibliography:
http://celtickane.com/rocketry/projecti/math.php
Appendices:
Refer to back pages
