One-Winged Fruits
Students’ Sheet
Introduction
Many fruits have a single wing. The seed is usually at one end of the wing, but in a few cases it is in the centre of the wing. The position of the seed affects how it moves when dropped.
The drawings on the right show examples. Each seed is attached to a paper-thin, rigid shaped wing.
A is an ash tree fruit. The seed is at the end of the wing that is attached to the tree.
B is an elm tree fruit. The seed is close to the centre of the wing.
C is a drawing of two fruits from a sycamore maple tree. When it dries out the two fruits break apart and fall to the ground separately.
In this activity you will investigate what happens when one-winged fruits fall from a tree.
Activities
Activity 1: Seed in the centre
It’s not as common as having the seed at one end of the fruits, but seed-centred fruits are known. Hoptree fruits and bushwillow fruits are examples.
If you did the activity ‘Winged Fruits’ you will have seen how a circle cut from paper behaves when it’s dropped. It flutters and spins to the ground.Let’s try it again and then add a ‘seed’ to the wing.
Cut a circle of paper about 6 cm in diameter. Hold it gently by its edge and let it go. How does it move?
Now add a ‘seed’. Mark the centre of the paper disc (if you don’t know how to do this your teacher will help). Take two small balls of BluTac, say about 2 mm in diameter, and press them on opposite sides of the paper, but both on the centre spot.
What affect does this have on the way the paper disc behaves when dropped?
Try some different positions of the seed on the wing.
Question
What do you think will happen when a one-winged seed, with the seed at the centre of the wing, breaks free from a bush?
Activity2: Monitoring the flight of sycamore fruit
Watch these short videos of sycamore fruits falling.
Your teacher may suggest others or you might be able to find them yourself.
Now read about these students’ investigation.
The students were given a number of sycamore fruits. The fruit had wings that ranged from 25 mm to 41 mm. In turn, each fruit was dropped from the viewing gallery of the sports hall and the time taken for it to reach the floor was recorded. Each fruit was tested three times and the mean fall time calculated.
Wing length / mm / 25 / 41 / 27 / 35 / 36 / 31 / 34 / 29 / 33Time to fall 3 metres / s / 4.1 / 2.7 / 3.8 / 2.9 / 3.1 / 3.4 / 3.1 / 3.5 / 3.5
Questions
1. Having looked at the videos, describe how a sycamore fruit falls from the tree to the ground.
2. Turning now to the students’ experiment:
(a) Describe the trend in the time to fall as the wing length increases;
(b) Make a scatter graph by plotting wing length on the x-axis and the descent time on the y-axis. Use a scale on the x-axis of 2.0 to 4.4 s and a scale on the y-axis of 20 to 45 m.
(c) Draw a straight line of best fit and measure its gradient. Explain why the points are close to, but scattered around this line.
If you have time and suitable fruit are available (late summer /early autumn), you could work with other students to carry out the experiment yourselves.
Activity3: How does a one-winged fruit ‘fly’?
You are now going to make two simple paper models that will help you to understand how a one-winged fruit descends.
Model 1
Cut a strip of paper 1 cm wide and 8 cm long
Put a paper clip on one end of the strip and, using your thumb and forefinger, put a curl and slight twist in the strip.The picture on the right shows what you are aiming for.This is your (very) simple model of a single-winged fruit.
Find a suitable place to drop your model fruit and the piece of plain paper that you will compare it with. Ideally you want to be as high as possible, but with little or no wind. The viewing gallery of a sports hall, for example, would be fine.
Drop your model seed (curled paper + paper clip) and the strip of paper. In each case, hold the paper horizontally by its edge and release it. If you want, you could time the descent. Repeat this several times.
Questions
1. Describe as fully as you can what happened when you dropped: (a) the flat strip of paper (no curl, twist or paper clip), (b) your model fruit
2. How did the movement of your model fruit compare with that of the sycamore fruit you watched in the videos?
3. Give some ways in which the wing differs from the wing of a dry sycamore fruit (think about words such as flexible, rigid, edge, thickness, shape, symmetry).
4. Give reasons for the way the model fruit descends when released.
Note: The aerodynamics of flight are complicated, so don’t expect to be able to give a ‘right’ answer. Just think about gravity and about the arrangements and movement of particles in solids and gases.
Model 2
If you look at a sycamore fruit you will see that it is inflexible wing with a thick ridge on one edge.
From a sheet of paper cut out a shape similar to that shown below. Fold along the dashed lines, creasing the folds firmly.
Now attach a 3 cm paper clip as shown in the second diagram.
Take your model somewhere that it can be safely dropped from 3 m or more.
Drop your model and watch its movement. If you have a digital camera or smartphone you could try recording it. Hopefully it will mimic closely a sycamore seed falling.
Questions
1. Describe as fully as you can what happened when you released your model.
2. How did the movement of your model fruit compare with that of the sycamore fruit you watched in the videos?
3. Give some ways in which the wing of your model differs from the wing of a sycamore fruit.
4. Give reasons for the way the model fruit descends when released.
5. Which of the two simple paper models you made best represents the structure and flight of a sycamore fruit? Give reasons for your answer.
Activity4: An origami model
This is a fantastic origami model that illustrates the movement of a one-winged fruit as it drops to the ground.
If you go to this website you can see a step-by-step demonstration of how to make the model:
Origami Maple Seed (DavorVinko)
There are several other videos available that show the model being made. Just try typing Origami Maple Seed into your favourite search engine.
It is a little fiddly to make and needs some patience first time around (these things are always easier after you’ve had one try). It’s worth the effort though.
Science & Plants for Schools:
One-Winged Fruit: p. 1