[Archive!] Pure mathematics, physics, chemistry, etc.: brain-training problems not related to trade in any way - page 456

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Richie:
Alexei, you are a smart man, can you explain to me why the Moon does not fall to Earth? For what reasons? At school I understood, but now I can't.
It is prevented from doing so by its own inertia - it sort of seeks to fly away from the earth tangentially all the time, but the force of gravity prevents it from doing so and returns it to an elliptical trajectory.
 
alsu: Let me explain - if our three things are placed so that there are only attractive forces between the magnets, the equilibrium is stable, if there are repulsive forces, the equilibrium is unstable. But in both cases it is an equilibrium, but in the unstable version, a small deviation in the position of the magnets causes the equilibrium to be lost and the system flies out of it.
Here. And we have the moon in stable equilibrium. And it doesn't seem to be going out of orbit yet.
 
alsu: It is prevented from doing so by its own inertia - it tends to fly away from the ground tangentially all the time, but gravity prevents it from doing so and returns it to an elliptical trajectory.
And you believe that 2 forces keep the moon in balance? One step to the left, one step to the right and the equilibrium is lost in a "geometric scenario" .....
 
Richie:
A step to the left -- a step to the right and the balance will be lost in a "geometric scenario" .....
yes
 
Richie:
And you believe that 2 forces hold the moon in balance? One step to the left -- one step to the right and the balance will be lost in a "geometric scenario" .....

aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa!!!!

One force, one!!!!!

If suddenly the velocity of the Moon decreases slightly - then its orbit will change, it will become lower, corresponding to a given rate of rotation. If the speed is increased, the orbit becomes higher. If the velocity exceeds some limit called the second cosmic velocity, calculated from the relation Kinetic_Energy_of_the_Moon>=Potential_Energy_Field_Ptvkb, the Moon will fly the fuck away. If the velocity is less than some limit at which the semi-major axis of the orbit becomes smaller than the radius of the Earth, then the Moon will fall on our heads.

 
Thank goodness the real speed of the moon in orbit is far from both the first and second limits, and neither a flight or fall scenario is foreseen in the next couple of billion years.
 
alsu:
Thank goodness the real speed of the moon in orbit is far from both the first and second limits, and neither a departure scenario nor a collapse scenario is foreseeable in the next couple of billion years.

foreseeable.

the moon is moving away from the earth over time.

 
sergeev:

foreseeable.

the moon gets farther away from the earth with time.

)))) not so soon.

http://forum.norcom.ru/index.php?showtopic=8579

5. The Moon is moving away from the Earth.
Factor in tides, energy conservation and kinetic momentum. Measurements taken over the last 25 years clearly show that the Moon's orbit is increasing and it is moving away from the Earth. Overall, this is happening at a rate of 4 cm per year. However, astronomers predict that when the Sun enters a red giant phase - in about 5 billion years - both the Earth and the Moon will come together again due to the influence of its enlarged atmosphere. During this period, the Moon will come as close to Earth as ever - it will be at an altitude of 18470 km above our planet at a point called the 'Roche limit'. Eventually, the Moon will be torn into pieces and scattered to form a grand ring of 37,000 km in diameter over the Earth's equator, similar to Saturn's ring.

 

For those of you who don't know, so you don't have to search the internet:

the nearer points of the Moon are attracted to the Earth more strongly than the farthest points, and the closer the Moon is to the Earth, the greater the difference. So, the Roche limit is the distance at which the difference in force grows so large that the Moon is just blown apart.

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