Asia-Pacific Forum on Science Learning and Teaching, Volume 3, Issue2, Article 3(Dec., 2002)
Russell TYTLER
Using toys and surprise events to teach about air and flight in the primary school
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Flight

Activities

A4 sheets of paper, paper clips, tape, cotton thread, freezer bags..

Paper drop
 An air resistance POE sequence. In pairs, drop:

Watch video 6: ordinary (1.17 MB) or high (11.8 MB) resolution (in Real Player format)

Whirlybird

Trace and cut out the whirlybird design shown below from A4 paper. Fold it.

What do you think will happen when you drop it ?Try it.

Challenge questions :

Can you modify your whirlybird to make it spin the other way ?

Design a whirlybird that takes as long as possible to reach the ground when dropped from head high. (You might consider varying size, number of clips, wing span .... )

Design a whirlybird that spins as fast as possible

.Concept development :

What have you learnt about air flow and forces and flying, in modifying your whirlybirds ?

Develop a list of useful bits of technology based on this principle. (Windmill.....)


1. Cut along the solid lines
2.Fold along the dotted lines in the direction of the arrows
3. Place a paper clip on the bottom

Watch video 7: ordinary (1.66 MB) or high (19.3 MB) resolution (in Real Player format)

Parachute
Construct a parachute using a freezer bag, or even a larger plastic bag, using cotton attached at the corners, with a plasticine model figure. Construct a parachute that will drop as slowly and steadily to the ground as possible.

Predict what will make a difference to the effectiveness of the parachute.

Try out your ideas - compare different parachutes and figure sizes and methods of attachment. It is a good idea to keep comparing your changes with a standard model.

Investigate the effect of cutting a hole in the canopy. How big a hole can be cut without ruining the parachute? What is the effect of the hole on:

Commentary

PAPER DROP
In the paper drop activity, most students will arrive at a conclusion that the air resists the A4 paper but that dropping it held vertically minimises the surface that is pushing through the air and hence it will drop quickly (at least initially, until it skews off course). Younger students will often say the crumpled paper drops more quickly than the A4 sheet because it is heavier. Density, or compactness, is often confused with weight, and this is a good opportunity to have that discussion. The book falls more quickly, of course. This is because it has greater weight to overcome the action of air on its surface. The real purpose of the activity, however, is the surprise and challenge offered by the fact the paper falls along with the book. The reason is that the book is pushing the air that would be resisting the paper on its own. It is not needing to force through air, and effectively falls as it would in a vacuum. I am reminded by this of the experiment conducted by Neil Armstrong on the moon, dropping a hammer and a feather to find they fall at identical rates in the absence of an atmosphere ¡ ÊK as argued by Galileo. Some people argue that the paper is in the book's slipstream, which is in fact the same explanation if you think about it. The argument that air comes round the back of the book because of turbulence, and holds the paper on, is unnecessarily complicated and I think incorrect, although there is some turbulence.
I had one 5 year old child explain this counter intuitive result very quickly and convincingly by pointing out that the paper acted just like another page in the book, and so would be expected to fall with it!
This activity can be productively extended by dropping the paper and book from a greater height - students are often convinced it would separate if given enough time - or by dropping it with the paper partly projecting out from the book. You can get some interesting turbulence / vortex effects by projecting it out a long way.

WHIRLYBIRDS
Whirlybirds are intriguing flying objects, and always cause surprise and delight for students who try them for the first time. The spinning movement is so unexpected.
The spinning effect is due to the action of air on the wings as it rushes past the dropping whirlybird. You can check this by holding the whirlybird and pushing up on one wing with your finger. The body moves back as the wing is forced up. Pushing up on the other wing has the opposite effect, and you can see that the net result is a spinning set of forces. Flipping the wings causes them to spin in the opposite direction.
The longer the wings, the slower the drop because of the uplift on the greater wing area. The more paperclips, the fast the drop and spin, because of the greater weight.
The challenge of constructing a whirlybird that drops as slowly as possible is more difficult than constructing one that spins fast, although the measurement problem here is more challenging.
As well as conceptual engagement, whirlybirds provide the opportunity for the development of students' knowledge of investigations; hypothesizing, fair testing, measuring, recording and reporting. Try varying the number of paper clips, and the wing length, separately. Timing the fall is difficult, and comparing different designs two at a time is probably the most productive thing to do if you don't have access to a stop watch and a balcony from which to drop them. To keep track of what is happening, students should modify one aspect at a time, and preferably retain each modified design to keep track of what is happening.

PAPER PLANES
The same exploration principle applies to paper planes. It is instructive to keep the different models with commentaries on their flight, so that ideas can be checked and recorded. The basic principle is that air rushing past the wings provide an uplift force which counteracts the downward pull of gravity. The plane flies with the wings slightly angled up, so that air rushes faster over the top surface of the wing compared to the bottom surface, causing a pressure difference (see Bernoulli, below). The question of balance of the plane is thus important, and paper clips can help with this, generally placed towards the front. The action of the flaps in causing the plane to soar, or dive, is similar in principle to the effect of air on the whirlybird wings as shown in the diagram below of a raised flap.

The back of the plane is forced down as the air stream is forced up, thus causing the plane to lift.

Copyright (C) 2002 HKIEd APFSLT. Volume 3, Issue 2, Article 3 (Dec., 2002). All Rights Reserved.