Why does the object's weight change when its altitude goes higher?

Answer 1

The weight changes because the object is further away from the center of earth where the gravitational field of earth is the strongest.

Answer 2

Weight is the normal force that counters gravity.
For example the weight of 1 kg of tomatoes on the earth's surface is N=gravitational force=mg=1*10=10 N (and not 1 kg which is the layman's definition of weight).
The gravitational force is nearly constant close to earth, but it actually changes according to F=GmM/r^2 where G is the gravitational constant, m the mass of an object on which the force is acting, M the mass of the earth and r is the distance from the earth's center.
Notice that since the distance from the earth's center is in the denominator then as we get further away from the earth's center (or surface) then the force decreases. If the gravitational force decreases the the countering normal force also decreases and so the weight changes.

Answer 3

Two reasons:

First: The buoyancy factor changes since the density of air is less at higher altitudes. The change is very small but the object weighs 'more' as the height increases.

Second: The weight decreases as the height increases since the acceleration due to gravity (earth's attraction) decreases. This is likely to predominate over the first effect

Answer 4

the gravitational force goes as 1/r^2. where r is the distance between the two objects. so you can see as r increases the overall value of the fraction decreases.

specifically,

F_grav = G*m1*m2/r^2

where:
m1 and m2 are the masses of the objects
r is the distance between the two objects
G is the unversal gravitational constant (6.67X10^-11)

Answer 5

it gets farther from the Earths gravitation pull and so it weighs less. Kind of like on the moon and in space things weigh less
because of a lower gravity.