Falling severe, "Apollo 15" and the speed of the rivers
Before the sixteenth century, before modern science was born from the hand of unique genius as Galileo or Newton (say a few names), science (and physics in particular) was an activity largely reflective. Physics was a physical away from experimentation (this does not mean that prior to the fifteenth century there had been great observers and experimenters, one example, Archimedes). During the Middle Ages, the prevailing thought was Aristotle was the last word of knowledge.
Aristotelian physics (it was Aristotle who coined the name of physics) had some pretty strange ideas in relation to the movement of the stars and the movement of bodies.
a particular idea was the free fall of bodies (the vertical drop of a body from a height). To Aristotelian physics, the decline was faster the more had a body mass. This idea was wrong. But it was assumed, in part (leaving aside the weight that had Aristotle) \u200b\u200bby the absence of experimentation.
However, fortunately for humanity, in the sixteenth century came the great Galileo to help us, and introduced full experimentation in science.
In fact, we now know, thanks to Galileo, that if we drop two objects of different mass from the same height in a space that no air (to avoid friction with air) the two once they reach the ground. The free fall of a body does not depend on its mass.
is said that to demonstrate this fact, Galileo dropped various objects from the Leaning Tower of Pisa. But as they fell very fast, he managed to slow the fall radically changing the design of the experiment, and that's when he made his famous experience of a slope.
Physics home of the "Apollo"
During the Apollo 15 mission, the mission commander, Dave R. Scott, took the almost total emptiness of the "atmosphere" to emulate Galileo lunar. For this he dropped from the same height a hammer and a feather: indeed, the two arrived at once (this proves to two things: that Galileo was right and that conspiaranoicos are wrong when they say that man walked on the moon). Before the cameras of the mission, it was proven once again that Galileo was right. Eppur si muove.
Basics
energy
What is energy? From a mechanical point of view, energy can be defined as a quantity that quantifies the ability of a body to develop strength, or to develop a movement.
With this definition in mind, is easy to understand that a body in motion, for the simple fact of moving, will have an energy associated with its state of motion. Indeed, this is what is called kinetic energy . And this energy is linked to the speed of the body.
However, this does not mean that a body at rest has no energy. If we recall the definition, says the "ability of a body to develop a movement." Whether a body is at rest, this does not mean it is not able to move or move to another body. Even the strong need rest!
Thus, the bodies will have, apart from the kinetic energy, an energy related to their ability to rest stop. This is what is called potential energy (ironic, that these terms of modern physics have their rationale in the distinction made Aristotle between power and act.) Example of potential energy
: suppose the hammer dropped the astronaut. At the time that the hammer is in the hand of an astronaut, not moving, the hammer has a potential energy, which depends on the distance separating it from the ground. The moment you let go, and falls, hits the ground with a speed: at the moment only has kinetic energy. All the potential energy becomes kinetic. The body has developed a movement, and potential energy in a way, was measuring how much movement we would be able to perform.
This serves to introduce another basic concept of energy: the principle of conservation of energy. Energy can be neither created nor destroyed. Can only be converted into other forms of energy. Sticking with the example of the hammer, the hammer was initially a potential energy, upon reaching the ground, all that potential energy was converted into kinetic energy. And after the impact, all that kinetic energy is converted into heat, more energy degraded.
Now we can move to the last thread of this article.
Where a river is faster?
A river is a natural system can be considered divided into 3 parts:
- The current high birth. That's where the river reaches its highest slopes, where we are waterfalls and rapids, where there is turbulence, where there is higher incidence of erosion ...
- The middle: where there is a balance between erosion and sedimentation. The slope is lower than in the previous case, and there is no such violent phenomena such as waterfalls.
- The lower course, the mouth. Here the river is nearly horizontal, and there will be a predominance of sedimentation processes.
Now I propose a riddle to a potential reader, who does not intend to spend a long time. Given the above, of those 3 parts, where the river will go faster?
In principle, observation and intuition suggests that where the river is more rapid in the upper, there are more pending, we fast, waterfalls, ... And in the mouth has to go slowly: the river is horizontal, and also that we can see that deposited material.
However, quite the opposite: the higher speeds are reached the river during low and high during the lowest.
Consider a water molecule in the birth of the river, there will be a certain speed (and thus kinetic energy) but also have a potential energy associated with its height relative to sea level (which remember, We measured the ability of the molecule and move down to the ground). When this molecule reaches the lower course of the entire potential energy was in the upper will have become kinetic, thus by definition of kinetic energy, the river will increase speed.
really the fact that the velocity is greater in the lower course contributes not only the issue of energy (in fact, really no influence, because the river bed varies from one area of \u200b\u200bthe river to another section of the channel varies, vary flow, ...) in the upper water follows paths turbulent, erratic, and although the speed of a stream of water can be very high, the various streams of water follow different paths, sometimes even some threads going upstream, upstream. In the lower reaches, however, is laminar flow, all streams of water follow the same direction. Consequently, the average velocity of flow in the lower reaches will be greater than the upper.
Anyway, not all ideas in Earth Sciences are intuitive. Good
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