Building a vehicle that runs as far as possible

Authors : Cécile de Hosson(plus d'infos)
Summary :
Participants are invited to make an object using simple materials, as an answer to the trainer’s challenge:" Build a small vehicle that runs as far as possible, without pushing it manually”. The training activity has several objectives: the realisation of the object with materials imposed by the trainer, the reflective analysis of the exchanges between participants, the identification of the main issues, in terms of the acquisition of scientific and technological knowledge and know-how. Through this activity, participants will experience the main steps of an investigative approach (elaboration of a construction protocol based on hypotheses, experimental tests, modification and optimisation of the object, separation of the variables influencing the movement, etc.). As a result of their conceptual and analytical work, participants conceive a lesson plan.
Publication : 13 September 2012
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Context

Theme: Training of primary school teachers on the investigative approach, on the basis of a activity aimed at children 7-11 years old, principally in the domain of technology: "Constructing a small vehicle that runs as far as possible, using imposed materials".

Audience: 20 primary school teachers

Duration: 6 hours

 

Preparation of the room:

1. Materials (the materials are placed on a table and visible to all):

  • skewers, sticks of wood
  • Corks and plastic stopper
  • Straws
  • Plastic 35 mm film canister
  • Balloons
  • Small empty plastic bottles
  • Glue, adhesive tape, cutter, scissors

2. Organisation of tables: 4 blocks able to accomodate 5 people each.

 

Unfolding

(Trainees are grouped in 4s/5s)

 

1st stage: The contextualized situation (30 minutes)

The trainer specifies the objectives of the training session. At this stage teachers do not touch the available materials because it could have the effect of reducing the value of the oral and written reflection.  However, they can study them.  They can refer to the document presented in Annex 1. In principle, participants will analyse in particular:

  1. The role of the pupil at each stage of the activity;
  2. The role and place of the teacher at each stage of the activity;
  3. Knowledge and competences acquired;
  4. Difficulties encountered (technical, scientific, educational);
  5. Proposed solutions.

 

Trainees are submitted to a complex task: they are asked to analyse their approach, both as students and as teachers.

 

2nd stage: The construction plan (1 h 30)

 

 

Each group draws and describes a car project without touching the materials. Trainees formulate technical solutions with justification, reasoned prediction or hypotheses:

  1. The mode of propulsion (example of prediction: the expulsion of air from the balloon causes the motion of the vehicle);
  2. The wheels (example of technical strategy: the skewer is the axis of the wheels that will make the wheels turn with it)
  3. The friction (example of explanation: frictions prevent movement)
  4. The mass of the vehicle (example of hypothesis: the greater the mass of the vehicle, the slower the car moves away)
  5. The rate of the air output (example of prediction: the slower the air goes out, the farther the car runs away).

For each group, the construction plan must be agreed by all members.  It is then "validated" by the trainer. In fact, the trainer only validates the feasibility of the construction, and not whether the car will run or not. Technical solutions and their justifications and hypotheses are discussed in the large group.

The momentum conservation principle - implied by the activity - is rarely mentioned by the participants in order to explain how the expulsion of air sets the vehicle in motion.  Most of them think that if the car moves forward, "it is because the air leaving the balloon presses the air outside the vehicle and that, in response, the air exerts a force on the vehicle that makes the vehicle move forward." In fact, the output (or loss) of a certain quantity of air through the opening of the balloon causes the movement of the vehicle in the direction opposite to that of the air outlet.  It is the same phenomenon that explains why a balloon filled with air, held at the open end and then released, flies in the opposite direction to the expulsion of air: the force exerted by the balloon on the air during the expulsion of air = force exerted by the air on the balloon (= principle of action and reaction). The presence of air outside the vehicle is not necessary. Note, however, this principle is not in the curriculum of primary school.

 

              

 

Principle of action / reaction within a balloon

 

 

Prediction phase concerning the movement of the vehicle

At this stage, the trainer moves from group to group and asks a number of questions that will be discussed later, by the group assembling all the participants, during the assessment phase (see below):

  • Why does the vehicle move?
  • In which direction does it move?
  • Would your vehicle work on the Moon?
  • Can you explain the principle underlying rockets’ take-off?

 

 

3rd stage: The construction of the vehicle (1 h 30)

As a first step, trainees construct their vehicle as in the construction plan presented to the trainer. After the first trial, they modify their prototype in order to obtain better performance. Some notice that:

1. The vehicle moves in the opposite direction to the one they initially predicted.

2. The wheels do not turn.

3. The mode of propulsion does not work

At this stage, trainees are completely absorbed in the construction activity and generally do not think of taking a reflective look on their approach and their activity (both conceptual and social).

 

 

Particular attention will be paid to the written records: if there are changes to the vehicle, then  the written record should include them.

 

4th stage: The groups present their vehicles (30 Min)

This presentation can be done in the form of a race. Each group presents its vehicle, justifies its technical choices, explains the changes that were made during trials, and gets ready for a race that will see all the vehicles contesting.

 

 

5th stage: Assessment (1 h)

Aims

1. Analyse the vehicles developed, the relevance of initial choices, the changes and the underlying scientific knowledge.

2. Analyse social processes brought into play in the development of the vehicle: conflicting debates, co-construction...

 

The analysis of vehicles focuses on the following scientific and technical aspects:

 

 Place of the balloon

Some put the balloon inside the bottle and notice that it is impossible to inflate it.  Trainees thus learn that the bottle is full of air, and that it occupies all the available space.
Some trainees predict that the vehicle will move in the direction of the movement of the air and place it accordingly

Mode of propulsion

All raise the question of the force that will cause the speed:
Most groups use the movement of air expelled from the balloon but do not know the physical principle of action and reaction (see above).

Wheels movement

Some stick wheels directly on the shell of the vehicle and find that to have a rotational movement of the wheels, it is necessary to make an axis and an axle (skewer placed inside a straw).

Friction

Some try to reduce the friction between the wheels and the floor and do not imagine that friction can enhance the movement.
Others raise the question of the friction relative to the air and of the aerodynamics of the vehicle.

Mass

Should the vehicle be light or heavy?

Trajectory

How to make the vehicle move in a "straight line"?

 

The analysis of social processes put in place during the activity is aimed at enabling trainees to identify the role of teachers and students respectively, the interest of the open debate and of co-construction. This stage leads to the elaboration of a lesson plan (see below). To this end, trainees can answer the following questions:

1. Was there a debate? When? Why?

2. How did you arrive at a consensus (authoritative argument, collective discussion...)?

3. What can be the place and role of the teacher in the management of group work? During the phases of collective discussions?

4. What is the place of verbal and written work respectively?

 

6th stage: Elaboration of a lesson plan for a class session (1 h)

Each trainee (not each group) is asked to elaborate the lesson plan of a session, for a class of his choice. To do this, each trainee may use the documents provided in annex 2.        (TO BE CONFIRMED BY THE AUTHOR)

The excerpt of the Accompanying Document for students aged 9-11 (see below) recalls the objectives of a construction activity. One could also refer to the objectives of the investigative approach (see below).

 

 

 


Annex 1

 

Building a vehicle that runs as far as possible using imposed material.

 

Description and justification of the choice of materials

Make a plan (paper-pencil)  for the construction of a vehicle, specifying and justifying each element:

1. Technique used;

2. Materials used;

 

Parts of the car

Techniques used/justification

Material used/justification

 

 

 

 

Evaluation of scientific knowledge involved (with the help of the trainer)

Specify, for each part of the vehicle, the physical and technical knowledge involved and the scientific principles that underlie the functioning of the vehicle. Connect each principle to the initial conceptions and difficulties it raises (yours and, supposedly, those of the students).

 

Evaluation of issues related to the co-construction of the project

The elaboration of the project is done in groups of 4/5.  For each phase of the discussion (to be explicitated), provide details about the exchanges and, above all, the arguments used. In case of disagreement, specify the conflicting positions. In case of consensus, specify the manner through which you reached that consensus.

 

Discussion phase

Agreement

Disagreement

 

 

 

 

Annex 2

 

 

Excerpt of the Document for the implementation of the science curriculum (age 9-11) , Sceren, 2002, available at this address.

 

 

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