What the Activity is for

This is a focussing activity, that shows the wide variety of things that fall in the children's everyday environment, and begins to develop a range of descriptions for these falls.

What to Prepare

• A frame for collecting lists of kinds of things that fall
• Frames for developing different kinds of descriptions of falling

What Happens During this Activity

Encourage children to collect examples of many different kinds of things that fall and seek to categorise those in ways that make sense to them.

Compare and contrast the different falls, seeking to develop a qualitative or semi-quantitative description of each.

The idea of a semi-quantitative description is useful here: we want to build to talk about more or less speed and more or less force.

You're not after full quantification, with numbers and units: we are after comparing the values of the speed over a journey (in this case a fall) and perhaps, somewhat later, the values of the forces over that same journey.

What the Activity is for

What causes a fall? What can change how a fall happens?

The purpose of this activity is to begin to ascribe changes in a fall to the forces acting on the object. The forces are identified by hunting down interactions between the object and its environment. Initially we suggest producing two parallel descriptions: one about the forces and one about the speeds or velocities.

What to Prepare

• a frame on which to describe the fall
• real objects to walk through a fall

What Happens During this Activity

Drop something (choose something interesting, that will not break when it hits the floor). Then walk through the fall very slowly.

Ask for each of three or four stages:

Teacher: What is happening to the movement of (this falling thing) just here?

The three or four stages should be chosen wisely. We'd suggest:

1. just as you release the object
2. a short while after the object is released
3. just before the object hits the floor
4. as the object hits the floor

For each of the falls, we suggest completing a number of different descriptions – written, a cartoon drawing, a simplified diagram with arrows. For each kind of description, we'd suggest trying to draw out the difference between the descriptions of the motion and the causes the motion (that is between the forces and the speeds or velocities). Two parallel frames are useful here.

You might extend this activity by selecting a number of objects which vary in the way they travel through the air, such as:

• a soft toy
• a small stone
• a feather
• a sheet of paper
• a screwed up ball of paper

Alternatively you might provide each of a number of small groups with a pair of dissimilar objects, and a printed copy of the frame. Each group should walk through the fall of both of their objects and agree on descriptions to write on the frame (a shared frame, A3 or larger, helps to promote discussion). The faster-moving groups could the encouraged to compare and contrast the two falls and their descriptions of these falls.

What the Activity is for

Different continent, different down?

Children often have a very local understanding of the word down. In this simple and short activity we invite them to consider what down might mean for children in different places on this planet.

What to Prepare

• a large globe, with the continents clearly marked
• a selection of small plastic toy people
• Some cardboard arrows labelled down, scaled for the people
• some cardboard force arrows labelled gravity
• a small stone
• a means of fixing the figures and arrows to the globe

What Happens During this Activity

Introduce the globe, and locate an individual toy person (perhaps named for somebody in the class) at your current location. Then build up to an experiment to determine the use of the word down.

Teacher: We're going to do very careful scientific experiment to figure out which way it down.

Teacher: We're going to concentrate on how we think about down. It's just the way things fall when we let them go. Let's try for this stone.

Teacher: So that's our experiment, now let's make a record of that on this globe.

Now reach for a labelled cardboard down arrow, and get someone from the class to add this arrow to the named plastic person.

Now imagine doing exactly the same experiment for a number toy figure on a different continent. First place the figure, and then do the thought experiment. You might make a better the fuss of the idea of a thought experiment, as being something that is done quite often in the sciences when you cannot actually go to a place or set up a situation to explore.

Alternatively, it is possible that you have a classroom link to a school in another country in which case a short video clip of their version of down might enliven the activity.

Teacher Tip: We advise against replacing the physical globe with any virtual representation of it on screen – the real three-dimensionality is important here.

Repeat for several continents, so that you have four or five small plastic figures and down arrows distributed across your globe.

As a next step you might add gravity arrows to each of the figure's locations, giving a reason such as:

Teacher: Gravity is the name that we give the force that makes things fall. wherever we see things falling, we expect to find the force of gravity at work. Things fall down, as we've seen. So the gravity arrows and the down arrows point in the same direction.

Finally you might produce a two-dimensional diagram of your globe, as a summary of what you've been doing.

It might help the transition to this diagram to cast a shadow of your three-dimensional globe and plastic figures on the wall in such a way that you can trace around it. Cunning forward planning will ensure that at least three figures and their arrows appear as clear shadows, and at very different locations on the globe.

What the Activity is for

'Down' on different planets.

Here you can explore how the idea of down varies as you move from one planet to another, from one planetary system to another, from one star system to another, or from one galaxy to another. Down depends on the local gravity arrows.

There are significant links between this activity and the activity Falling all over the world which can be exploited.

What to Prepare

• large spectacular images of clearly separated astronomical objects, perhaps shown using a data projector
• a selection of small plastic toy people – astronauts, if possible
• Some cardboard arrows labelled down, scaled for the people
• some cardboard force arrows labelled gravity
• Balls of different diameters to model planets

What Happens During this Activity

Start with showing the large image. Add the astronaut, and ask:

Teacher: If she dropped something, which way would it fall?

Then build on the answers to add a down arrow at this location. Move the astronaut around the astronomical object, repeating the question and discussions to leave a trail of down arrows around the astronomical object, at a variety of locations surrounding the object, at a number of distances from the centre.

As a next step you might add gravity arrows to each of the figure's locations, giving a reason such as:

Teacher: Gravity is the name that we give the force that makes things fall. Wherever we see things falling, we expect to find the force of gravity at work. Things fall down, as we've seen. So the gravity arrows and the down arrows point in the same direction.

We'd suggest repeating this for a number of distinctive astronomical objects, from planets, through asteroids, to the stars and moons.

At several stages you might add in a three-dimensional model using one of the balls and a number of astronomical figures. It all depends on how well you think the transition between the three-dimensional and two-dimensional is progressing.

As a summary of the whole exercise you might produce a two-dimensional diagram, where the central object is deliberately labelled as a number of astronomical objects explicitly. Surround this with a number of pairs of down and gravity arrows. Add astronomical figures as observers if that seems to make this thought experiments more concrete.

You might supplement this activity with some video clips of people dropping things in space: just make sure the people and the camera are not falling as well to avoid conceptual difficulties.

What the Activity is for

The idea here is a bit subtle: we are working with the ideas that falling is simply a kind of motion, and that all motions are relative. So falling itself is relational. In particular if two things are both falling together, then there really is no relative motion. This is no different from being unsurprised to find that your passenger in the car is still beside you after several miles of journey: you are moving together – moving past the scenery, but not moving past each other.

What to Prepare

• two soft toys
• a chair, ladder or balcony to give you a free-fall distance of around 2 metre

What Happens During this Activity

Start by telling a story about the two soft toys going on a journey, just walking across the table top, or through the undergrowth, or across the lawn. If they walk together, hand-in-hand, or side-by-side, then they're travelling at the same speed: they don't move apart or separate.

Then switch the kind of journey to one where they are falling, perhaps a kind of controlled falling in a lift to start off with. Again emphasise that they fall together – there is no relative motion.

Develop this to put them in free fall. Talk through their journey again from the point of view of first one and then the other. What will each one see? If technology permits you might equip one with a small video camera to record a fall. Practice will be essential, so that you do get a clear video of the other toy falling beside the first one.

You might supplement this with videos taken by skydivers, as they fall together.

To take it further, look for such a video where one skydiver opens his parachute. This really drives home the idea that motion is relative – the camerawoman keeps on falling, the other appears to shoot upwards – but of course that's just the relative motion in action.

With practice and for a bit of fun, you might manage to reproduce this with your soft toys and video camera.

What the Activity is for

Same speed: changing speed. Here we revisit the walk-throughs of falling, with a careful emphasis on noticing the changing speed.

What to Prepare

• a dandelion seed, or downy feather
• a frame for recording the speeds over the fall

What Happens During this Activity

Drop the Seed or Feather, and ask for a careful description of how it moves. Focus on the vertical movement – just the falling.

As before, split the motion into several stages.

1. just as the feather or seed is released
2. just after the feather or seed is released
3. a long time after the feather or seed is released
4. a very long time after the feather or seed is released

In this case would suggest that you avoid including the collision of the feather of the ground.

The idea behind choosing a feather or seed is that it very clearly speeds up and then drifts down at a more or less constant speed for the remainder of the fall. You could verify this, at least approximately, by making regular marks on a whiteboard past which the feather or seed falls. For the majority of the journey these will be evenly spaced, showing a constant speed.

As a summary of the discussion about the motion of this object, we suggest producing a large frame, with written descriptions of the speed and arrows to show the speed at each of the four stages.

What the Activity is for

This is a compare and contrast activity. Compare the fall of the seeds that have evolved to fall slowly with those that have not. As we already have a description of motion for the slow falling seeds, you might reasonably expect the faster falling seeds to show the same pattern, even though our eyes are not up to the task (although a high-speed camera is).

What to Prepare

• sycamore seeds
• dandelion seeds
• a dried pea or bean, as a seed that does not float
• a frame for recording the speeds over the fall

What Happens During this Activity

Drop the dandelion seed, and summarise its motion over the four stages, drawing on the previous activity. We'd suggest here focusing on a description using arrows rather than words.

Drop the sycamore seed, and produce a summary of its motion. Its journey time is somewhat shorter, given that you have dropped it the same height, so the speeds will all be somewhat larger. You will need to develop the idea that the arrows will all be a bit longer through discussion, perhaps drawing on everyday journeys closer to home. the idea is essentially simple – that longer arrows lead to a shorter journey time: you cover more metres in each second.

Now might be the time to do a bit of predicting. Produce the bean seed and ask:

Teacher: We've got the patterns for the sycamore seeds and the dandelion seeds. What will the pattern look like for this been seed? In what ways will be different from the other two seeds?

You will need to run some discussion in order to develop the idea that the pattern is the same, but though there is some systematic variation across the seeds. Being able to line up all three completed frames will help you to establish the pattern, and to see the variation.

What the Activity is for

Rising – the same physics as falling?

Here you are going to extend the description of motion that you have evolved for falling to things that rise. SO this is something of a reinforcement activity, showing how the ideas can be reused in a describing a new process.

What to Prepare

• some cooling oil in a clear tall container
• a means of introducing bottles to the bottom of the cooking oil
• a Cartesian diver
• small stones, that fall through the oil
• a frame for recording the speeds over the fall or rise

What Happens During this Activity

Start by dropping the stones in the oil. Revisit the falling frames to record the changes in speed as the stone falls, again over the four stages:

1. just as the stone is released
2. just after the stone is released
3. a long time after the stone is released
4. just before the stone reaches the bottom

Make bubbles, and then ask for suggestions for completing the frames for the bubbles. We suggest the following four phases of such frames, as then the pattern will be directly comparable with the falling stones:

1. just as the bubble is released
2. just after the bubble is released
3. a long time after the bubble is released
4. just before the bubble reaches the top

Now complete the frames and compare the patterns. You should be able to flip one pattern to get another. The movement of rising bubbles are just the opposite of falling stones.

We'd suggest leaving the reason why this is the case as open at the moment – interesting, but not worth pursuing at the moment.

As an extension, you might consider using the Cartesian diver, which allows both rising and falling, and can therefore show both motions. You should avoid the temptation to explain how the Cartesian diver works – here it just provides a convenient process to study.

What the Activity is for

Here we start to look at forces that can oppose the gravity force and so prevent falling. This is a very simple quick introduction, and could be optional, but does open up the possibility of discussing some of the variation in speed over a fall.

What to Prepare

• A soft toy, or other object to focus on
• Some string
• Some weak elastic
• Some soft foam
• Some cardboard gravity arrows
• Some cardboard support arrows

What Happens During this Activity

Start by dropping the soft toy, this time focusing on the force of gravity that causes the falling. Building on this start, now open up a new question:

Teacher: How can we stop the soft toy falling?

Move the discussion towards providing some support for the soft toy: later these will be formalised as support forces, but that is a step beyond what you should aim to achieve here.

The endpoint of this discussion is simply to suggest that there could be forces which oppose the gravity force. These forces arise from the physical environment. It is useful to have a physical environment which distorts in order to provide the force, so we'd suggest starting with supporting this toy by using soft foam or by using weak elastic.

It is a further leap of the imagination to see the string as distorting to exert a force (a tension force), or to see the tabletop or floor as distorting to exert a force(a compression force). That is a step which may or may not prove useful for you to take.

The situation where there is no change in speed, because there is no speed at any time, is a special case of equilibrium: the forces acting on soft toy add up to zero.

What the Activity is for

There you can see the universality of gravity: there will be force arrows on all falling objects.

What to Prepare

• A wide variety of objects to drop (avoid anything fragile)
• A set of cardboard gravity arrows

What Happens During this Activity

Drop the objects one at the time, and walk through their falling journey. Choose any point on this walk-through other than the beginning or the end of the journey.

For each of the objects in turn, run a discussion such that the endpoint is adding a gravity force arrow to the object. Ensure that you have plenty of gravity force arrows so that at the end of the activity you can have an array of objects, displayed to show the gravity arrows on the objects at some stage during a fall (perhaps deliberately at various stages of the fall).

What the Activity is for

Here you can make the point that an constrained free fall is similar to just floating along in a current (and perhaps to just drifting along in outer space). It's all kind of natural motion.

What to Prepare

• Images of pairs of objects falling
• Images of pairs of objects floating in a current

What Happens During this Activity

Compare and contrast the images drawing on earlier work on relative motion to explore the idea of what might be an natural motion: that is something which objects to do by themselves when left alone in the environment.

This idea of a natural motion is a central one to develop later. Here it's just worth opening up the questions. It cuts to the core of understanding the universe as Newton did rather than as Aristotle did. And there's plenty of evidence that many people reason as Aristotle did in everyday life (because that's a successful way to reason), but fail to flip to reasoning like Newton did when engaging in more formal thinking in the sciences. Imagining motion with no forces acting turns out to be hard work, and to produce counter-intuitive results.

What the Activity is for

Do heavier objects fall faster? The purpose of this activity is to challenge the commonly held, but mistaken, idea that heavier objects necessarily fall faster than lighter objects. The detailed reasoning is for the future, but a start on establishing some thinking along the right lines can be made now.

What to Prepare

• Two blocks of wood, one at least double the mass of the other
• Two items of soft fruit – we'd suggest a melon and a peach
• A chair, ladder or balcony to give you a free-fall distance of at least 2 metre (more is better, but messier)

What Happens During this Activity

Start with hefting the blocks of wood.

Encourage children to predict which of two blocks will hit the ground first when released together from the same height. Allowing children to feel the different masses before release is important. Encouraging a dialogue about which of the two is being pulled with a greater force is also important.

It is likely that a range of predictions will emerge from the class. Invite children to share their reasoning for these predictions before they see the event.

Safety note: Take care when dropping heavy objects. Bouncing masses can be dangerous, as indeed can be falling ones. Two blocks of wood, about 200 gram and 800 gram, will do the trick and will not be adversely affected by wind resistance over a fall of a few metres.

Dropping a melon and a peach together from a significant height (a second floor window is likely to prove suitable) will provide memorable proof that the mass of an object makes no difference to the rate of fall.

You should be aware of the mess which will be created by this demonstration. This can be minimised by placing a large plastic sheet on the ground. You also need to be aware of the fact that from too small a height the fruits will remain intact (no sensational explosion), while if they are dropped from too great a height air resistance might become significant and the two will not reach the ground simultaneously. The moral here is that practice makes perfect. This is certainly one of those demonstrations that makes physics fun and simply unforgettable!