Theoretical and experimental capsule on the circle

Properties of the circle

Exercise

• Find several round objects and measure their perimeter

• How did you go about measuring round objects?

• Is this method precise?

Exercise

• How to measure an irregular roundish object?

• Is it easy?

• Do you know of an instrument to measure that kind of shape?

The Odometer

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Principle of the map odometer

0 km 10 km5 kmÉchelle de la carte

Molette

Point de repère

carte routière

Molette

Manche

Vue de face

Manche

Molette

Axe

Point de repère

Description of the principle

The wheel rolls on the map and allows you to accurately follow an outline or course. Using the reference indicator, it allows you to add up the number of kilometres traversed. Usually it is subdivided into equal parts in relation to the scale.

a b

Circonférence = distance ab

0 km 10 km5 kmÉchelle de la carte

Molette de 10 km subdivisée en 10 pour plus de précision. Chaque division représente 1 km.

Échelle de la carte0 km 10 km5 km

Circonférence = distance ab x 2

10 km

5 km15 km

0 km

Molette de 20 km subdivisée en 4. Chaque division représente 5 km et chaque tranche pourrait être à son tour subdivisée.

a b

Principle of the map odometer (continued)

Analysis of the technical object

• With what is it made? • How does it work?• What are the scientific principles that

explain the function of the odometer?• Where are (is) the force(s) that act on

the object? • Do they cause movement? • How is the movement transmitted?

Function

ForceHandle

WheelAxle

Forces

• I must push…

Movement

• …so that the wheel of the odometer turns.

Scientific principles

• I must push…

Movement

What is a wheel?

• It is a simple machine• The wheel was created long ago. It is used to circulate without

there being too much friction. Friction is where two surfaces rub together. It is also a part of many objects (the pulley, the gear, the friction wheel). It is, in a way, composed of a series of levers laid out over 360° where the support point is the axle of the wheel.