Site for children

J. Perelman
"Entertaining physics". Book 1.
Chapter 2. Gravity and weight. A lever. Pressure


What a load you can lift by hand? Assuming 10 kg You think these 10 kg determines the strength of the muscles of your hands? Wrong: the muscles much stronger! Observe the action, for example, so-called two-headed muscle of your hand. It is attached near the fulcrum of the lever, which is the bone of the forearm, and the load acts on the other end of the live lever. Distance from load to point of support, i.e., to the joint, almost 8 times more than the distance from the end of the muscle to support. Therefore, if the load is 10 kg, the muscle pulls with a force that is 8 times greater. Exploiting the power of 8 times larger than our hand, the muscle would directly raise 10 kg and 80 kg

Forearm With man - lever of the second kind. Operating force applied to the point I; bearing lever is located at the point O articulation; overcome the resistance (load R) is applied to the point In. The distance AT greater distances IO about 8 times.
(Figure taken from ancient writings on the market, the Florentine scholar of the seventeenth century, “On the motion of animals, where the laws of mechanics for the first time attached to physiology.)

We may, without exaggeration to say that every man is much stronger than himself, i.e. that our muscles develop strength, much more that which is manifested in our actions.

Whether such a device? At first glance, as if not, we see here the loss of power does not reward. But remember the old “Golden rule” mechanics: what is lost in power, won in the movement. Here is a speed benefit: our hands are moving 8 times faster than control their muscles. The method of attachment of the muscles that we see in the animal body, provides the extremity fine motor skills movement is more important in the struggle for existence, rather than power. We would be extremely slow beings, if our arms and legs were not arranged according to this principle.

Entertaining physics J. Perelman


System Orphus


Did you like our site and you would like to support it? It's very simple: tell your friends about us!

  © 2014 All children