Mechanical percussion

In Mechanic, when the force F becomes infinite during one moment infinitely short T, one speaks about percussion P = F.T.

In the modern notations, P = FT. \ delta (T) , notation of Dirac.

The unit of percussion is that of the momentum, Newton.seconde or Descartes.

In the same way, one will speak about moment at the point O of a percussion M = Mo \ delta (T) .

It follows an instantaneous variation of the kinetic torque, which is increased of this torque of percussion.

Theorem of Carnot

There is consequently discontinuity speeds. Thus discontinuity of the kinetic energy.

The theorem of Sadi Carnot indicates how to connect this discontinuity to the torque of percussion.

cf Call, or Whittaker for example.

Example: the hammer

There exist tens of hammers, each one with their function.

In the same way, there exist all kinds of nozzles (of bird).

Provost makes a good description of it; like Bouasse.

History of sciences

One plays billiards since the Middle Ages.

One plays certainly balls since longer.

Finally and especially, one makes the war with swords, lances and shields: the quintaine is practiced for the dubbing. The fencing masters learn how to box the percussions and the handles of the swords are carefully studied.

At the beginning of the 17th century, the increase in the duels results in thinking of the Center of percussion: question raised by Mersenne with the young whole Huygens (1629-1695), which will answer it magistralement with its theory of the pendulum weighing and the ballistic Pendule.

But especially, the thought of a law of dynamics is found via the percussions and discrete mechanics: all the drawings of the time testify some. It is by passage in extreme cases and continuation that m \ DeltaV = P, Newton will pass to me a' = F .

It rather that this subject is found at the end of the course, or even is thus curiously neglected, except by the trades of Industrial Sciences.

For the historians of proto-mechanics, it is absolutely essential to have with the spirit the work of the school of Galileo (1568-1642), and in particular of Torricelli (1608-1647), then of Huygens.

See too

Random links:Cademene | Omelet valley of Trough | Ebers papyrus | Saint-Laurent-of-water | The Rumor (film) | Christopher_Bond