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Mechanical clock HTML5


Brought to you in cooperation with the Musée des Arts et Metiers - Paris.

The principle of operation of all mechanical clocks rests on the combination of the following three functions:

  • A source of energy that can produce rotary motion (here, a driving weight)
  • A regulator:  A pendulum measures time precisely and without variations. The escapement system, linked to the pendulum,  enables control of the rate of energy release.
  • A display:  graduations and needles ("hands") provide access to the measured information.

Escapements generally use an anchor, as shown in this animation. For small angles (<5°) of oscillation of the pendulum, one approaches the condition of isochronism:  the pendulum's period depends practically exclusively on local gravitational conditions and the length of the pendulum (bit not on either the mass of the pendulum or the amplitudes of its oscillations).  For example, in Paris, a meter long pendulum has a period of two seconds. Lengthening the pendulum increases its period of oscillation.

Click and drag the slider to modify the period of the pendulum.

Wind up the clock by lifting the weight.

Learning goals

  • To simulate the operation of a device that permits the measurement of time.
  • To approach the history of this invention (Galileo, Huygens, George Graham...)
  • To show an application of the periodic motions of a pendulum.
  • To illustrate the principle of operation of a coupled anchor-wheel escapement (control of energy)

Learn more

The need to measure time precisely marks human history. We can distinguish between two different problems on this score:

  1. Long term measurements used to divide the year or the month into days…

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