You can really weigh more or less Based on the place where you are? Yeseven if little. Let’s assume that we make a truly unusual journey: we take a plane to the equator and cross the northern hemisphere to reach the North Pole. But first we have to weigh us And then once landed, always with the same scale (since we are scientists and we want to do things well) we weigh again. The value that we read on the scale change? Yes, the results are clear: to the poles (north or south they are) We weigh more than to the equator Even if our mass does not change … but why? It’s all fault of the ellipsoid form and centrifugal acceleration of the earth.
The weight changes because of the rotation
The weight of an object is his mass for the acceleration of gravity (P = mg). This is what they teach us at school and that we read on books … and so far everything is ok.
There mass It is an intrinsic property of a body and it is always the same throughout the universe, instead the acceleration of gravity (g) no (so much so that the one on the moon is different from that on earth, for example).
The problem of the different weight exists when we take it for granted that the acceleration of gravity is uniform throughout the globe and equal to 9.81 m/s2. It is therefore not a mass problem, but of acceleration of gravity due to shape of the earth.
We know well that the earth is not uniform: overall we can say that it is more crushed to the poles and more “wider” to the equator, it is not perfectly spherical Although we often see it represented so by practicality. But what is this effect due to? At the terrestrial rotation.
Since the earth is rotating, thecentrifugal acceleration (that force that tends to “shoot” outside the objects that rotate) changes the value of the acceleration of gravity: this means that that famous 9.81 m/s2 it is not valid everywhere but It depends on where we are. At the poles, G apps on average 9.83 m/s2 While the G -equator is around the 9.78 m/s2.
At the poles this value is greater than what we would measure the equator because of the terrestrial rotation effect. Quantitatively we speak of a minimum variationbut still measurable: to the poles “we add” About 0.5 % of extra weighteven if our mass does not change. We could summarize by saying that finding ourselves closer to the center of terrestrial gravitation, We suffer gravity more at the poles Compared to the equator, where we are further away than it. This is because the more you move away from a mass, the smaller is the gravity that it exercises on us (and that we exercise on it). Furthermore, the effect of centrifugal acceleration to the equator slightly contrasts the gravitational attraction, decreasing its intensity.
We conclude the discussion with a further question: if we weighed on the ground or On a plane, it would still change something? Certain. Since the distance from the earth makes the weakest attractionat high altitude we weigh less, as if we were at the poles.
