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

WHERE THINGS HARDER?

The force with which a body is attracted to earth, decreases as the elevation above the earth's surface. If we raised kilo weight to a height of 6400 km, i.e. remove it from the center of the globe on two of its radius, the force of gravity would fail in 22, i.e. 4 times, and a weight on a spring steelyard would pull just 250 g instead of 1000. According to the law of gravity globe attracts external body as if all its mass was concentrated in the center, and the force of this attraction decreases inversely as the square of the distance. In our case, the distance of the weights from the center of the Earth has doubled, and because of the weak attraction 22, i.e., four times. Removing the weight on 12800 km from the earth surface, i.e. at triple the distance from the center of the Earth, we would weaken the attraction 32, i.e. 9 times.

1000-gram weight would weigh only 111 grams, etc.

There is the idea that, venturing with weight in the bowels of the Earth, i.e., bringing the body to the center of our planet, we should see an increase in gravity: the weight in the depths of the Earth should weigh more. This conjecture is incorrect: with a hollow in the Earth body does not increase in weight, but on the contrary, decreases.

The reason is that in this case, the magnetic particles of the Earth are located on one side of the body, but on different sides. Look at the picture.


Why with a hollow in the Earth the force of gravity weakens.

You can see that the weight placed deep in the Earth, drawn down by the particles located below the weights, but at the same time is drawn up of those particles that lie above it. You can prove that ultimately matters is capturing only a ball whose radius is the distance from the centre of the Earth to the location of the body. therefore, the weight of the body as depressions in the Ground would quickly decrease. Reaching the center of the Earth, the body will completely lose weight, become weightless as the surrounding particles cause its there in all directions with equal force.

So, just more body weighs on the surface of the Ground; remove from her high into the weight decreases [As would occur if the globe was quite homogeneous density: in fact, the density of the Earth increases with approaching to the center; therefore, the force of gravity when going deep into the Earth first, at some distance, growing, and only then begins to weaken.].

Entertaining physics J. Perelman

 




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