Pratique du Shadowing: How Long Can You Balance a Pencil? - Apprendre l'anglais à l'oral avec la vidéo
Création de la leçon...
1
Balancing a pencil or any other top -heavy object on its tip is quite a precarious task.
2
It's easy to see why top -heavy objects are unstable.
3
They just want to fall down.
4
Any little nudge will put it off balance, with gravity happy to pull its center of mass even more off balance.
5
And the more off balance it is, the more gravity pulls until...
6
Physicists call this kind of tipping an inverted pendulum, because it's kind of like an upside -down pendulum.
7
And, careful mathematical analysis of inverted pendulums will tell you the obvious.
8
They're really unstable.
9
In fact, these equations predict that
10
if a perfectly balanced pencil with a perfectly sharp tip were
11
to get nudged off -balance by just one ten -thousandth the width of an atom, it would take only three seconds to fall over.
12
There are indeed acrobats who can balance poles with other acrobats on top, and robots that can balance and catch and throw upright sticks,
13
and people who make seemingly impossible artistic rock stacks.
14
But in all these cases, keeping the objects balanced either requires an active stabilization effort, or else carefully taking advantage of the fact that the balancing point isn't actually a point.
15
So the question is this, can you balance a pencil sharpened to a perfect single atom -wide tip on its tip without active stabilization?
16
Well, to start, you'd better get rid of all the air bumping off the sides of the pencil, since the kinetic energy of a typical oxygen molecule is enough to destabilize the pencil.
17
Remember, if the pencil gets off -center by even one ten -thousandth the width of an atom, it'll fall down in under three seconds.
18
And you'd better cool the pencil and table down as close to absolute zero as you can, since the thermal jiggling of their atoms when they're hotter will similarly jiggle the pencil off -balance.
19
But even then, matter at very small scales has a spread -out, wave -like nature, which means you can't have both the pencil perfectly upright and not moving at the same time.
20
And while this quantum effect is never a real -life inhibitor of precarious pencil balancing, it means you never even could succeed.
21
However, it's still fun to see how long you can keep a pencil balanced on your fingertip.
22
The shorter the pencil, the harder it is.
23
My best time for a standard 19cm pencil was 1 .3 seconds.
24
Think you can beat it?
À propos de cette leçon
Vous vous entraînez en anglais avec "How Long Can You Balance a Pencil?" en utilisant la technique du Shadowing.
Qu'est-ce que la technique du Shadowing ?
Le Shadowing est une technique d'apprentissage des langues fondée sur la science, développée à l'origine pour la formation des interprètes professionnels. Le principe est simple mais puissant : vous écoutez de l'anglais natif et le répétez immédiatement à voix haute — comme une ombre suivant le locuteur avec un décalage de 1 à 2 secondes. Les recherches montrent une amélioration significative de la précision de la prononciation, de l'intonation, du rythme, des liaisons, de la compréhension orale et de la fluidité.