Weight on Neptune: basics of physics
Let's imagine moving to Neptune for a moment with a friend of ours and two scales: a modern bathroom scale and a more traditional two-armed scale. If we both climb onto the latter, each on a different plate, the scale hangs on the side of the more robust, exactly as on Earth. Apparently, therefore, nothing has changed. it is very different from that on Earth. Why?
The weight of a body is the value of the gravitational force exerted on its mass.
The mass depends only on the quality and quantity of matter of which the body under examination is made up.
The mass, therefore, is identical wherever we are and that is why an object heavier than another on earth is also the same on Neptune. The weight, on the other hand - being subject to gravitational force - is a "variable entity:
Weight (N) = mass (Kg) by gravity (m / s2)
What we commonly call "weight" is therefore the force (of gravity) with which the Earth draws us to itself.
But what is gravity? It is a phenomenon whereby bodies attract each other with a force proportional to their masses and inversely proportional to the square of the distance that separates them:
Force of gravity = G (Newton's constant) x First body mass x Second mass
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(Distance between the two bodies) 2
Since the Earth is slightly flattened at the poles, the distance between a point on the Earth's surface and the center of the Earth is different depending on whether you are at the equator (where it is greater) or at the poles (where it is smaller). for this reason (the effect of Earth's rotation should also be considered) we weigh more at the poles than at the equator.
On Earth the force of gravity is equal to about 9.81 m / s2 (1 g), while on Neptune, being its mass slightly higher than that of the Earth, the force of gravity is equal to (1.14 g). Our weight on Neptune is therefore 1.14 times less than on Earth.
PLEASE NOTE: by convention we express the weight in Kg instead of in Newton (N) because in reality we translate this force into another unit of measurement, the "Kilogram Weight" (kgp or simply kg), which is equivalent to about 9.81 N ( 1 g). Therefore, on Earth a man with a mass of 70 kg weighs (70 * 9.81) 686.5 N or 70 kgp (686.5 / 9.81). On Neptune, however, the same man of mass 70 kg weighs (70 * 11.18) 782.6 N or 79.78 kgp (782.6 / 9.81).
