Friction, elastic impact and the fate of living force (vis viva)
In mechanics, friction was treated as a force opposing motion, and living force (vis viva) was taken to be lost in friction and in elastic impact. Helmholtz, in 1847, called this an incomplete account and asked whether the heat and electricity produced make up the loss.123 Later authors used friction to model damping, delay and heat production in living systems.457
- Earliest held
- 1847, Helmholtz, H.
- Most discussed in
- Principles of General Physiology, 1915
- In the library
- 225 passages in 36 works
- Rewritten
- 2026-10-29
Helmholtz's objection
In Über die Erhaltung der Kraft (1847), Helmholtz noted that mechanics usually presents friction as a force opposing existing motion, with an intensity that depends on velocity.1 He called this a calculating device and a very incomplete description of a complicated process in which many molecular forces interact.1 From that view it followed that living force was absolutely lost in friction, and the same was assumed for elastic impact.2 Helmholtz replied that the heat gained, and the electricity usually produced, are themselves forces that can yield mechanical effects. He therefore left open whether their sum always equals the mechanical force lost.3
Friction as a model
Bose (1902) studied a torsional pendulum struck by a blow and varied its friction by raising a vessel of sand against it. More friction damped the oscillation and gave recovery curves he compared with those of nerve, muscle, plant and metal.4 Bayliss (1915) used a weight on glass as a model of a catalyst. Friction can be so great that no movement shows until oil is applied. He said the question was nearly one of words, since the weight may move and be arrested again.5 Lotka (1925) placed systems with both inertia and friction between free and fully damped systems. Their action may resemble a pendulum swinging in air, and typically their history shows damped oscillations.6
Heat in muscle
Hill (1926) described reversible temperature changes in stretched or released muscle, first described by Kelvin, and found them in resting muscle. He also found large irreversible heat production when a muscle was stretched or released.7 Hill tied this heat only to the frictional transformation of mechanical energy into heat in a viscous system. It led him to the hypothesis that the energy loss he needed to explain was largely due to such frictional causes.7
Friction in free-energy models
Friston and Ao (2012) treat friction within a mathematical account of free energy, value and attractors. In their formulation it appears as a motion-dependent reduction in the rate of change of velocity. They state that friction is an emergent property of random fluctuations in velocity and nothing more.8 Here friction is not an extra force added to the dynamics. It follows from the random fluctuations the model already contains.
Man pflegt in der Mechanik die Reibung als eine Kraft dar- zustellen, welche der vorliandenen Bewegung entgegenwirkt, und deren Intensitat eine Function der Geschwindigkeit ist.
Helmholtz, H., 1847 · Über die Erhaltung der Kraft · open at passage 40Aus jener Auffassung folgte, dass bei der Reibung lebendige Kraft absolut verloren ginge, ebenso nahm man es beim elastisclien Stosse an.
Helmholtz, H., 1847 · Über die Erhaltung der Kraft · open at passage 40Es bliebe also [27] zu fragen ttbrig, ob die Summe dieser Krafte im- mer der verlorenen meckanisclien Kraft entspricht.
Helmholtz, H., 1847 · Über die Erhaltung der Kraft · open at passage 40If the friction is increased, there is a damping of oscillation. In (ce) we get recovery-curves similar to those found in nerve, muscle, plant, and metal.
Bose, J. C., 1902 · Response in the Living and Non-Living · open at passage 210The friction between the weight and the glass may be so great that no movement appears to take place until oil is applied.
Bayliss, W. M., 1915 · Principles of General Physiology · open at passage 1347Their action may resemble that of a pendulum swinging in air; typically the history of such a system exhibits the phenomenon of damped oscillations, a periodicity over which there is superimposed the dying away of the motion.
Lotka, A. J., 1925 · Elements of Physical Biology · open at passage 145These could be associated only with the frictional transformation of mechanical energy into heat in a viscous system, and they led us to the hypothesis that the loss of energy which we required was due largely to such frictional causes.
Hill, A. V., 1926 · Muscular Activity · open at passage 14Note that friction is an emergent property of random fluctuations in velocity (and nothing more).
Friston K, Ao P, 2012 · Free energy, value, and attractors · open at passage 56
| 1915 | Principles of General Physiology · Bayliss, W. M. | 34 |
| 1847 | Über die Erhaltung der Kraft · Helmholtz, H. | 25 |
| 1992 | On Growth and Form · Thompson, D. A. W. | 21 |
| 1918 | Life Movements in Plants · Bose, J. C. | 16 |
| 1925 | Elements of Physical Biology · Lotka, A. J. | 12 |
| 1926 | The Nervous Mechanism of Plants · Bose, J. C. | 11 |
| 1906 | Plant Response as a Means of Physiological Investigation · Bose, J. C. | 10 |
| 1928 | The Motor Mechanism of Plants · Bose, J. C. | 10 |
| 1913 | Researches on Irritability of Plants · Bose, J. C. | 10 |
| 1923 | The Physiology of the Ascent of Sap · Bose, J. C. | 10 |