A man whose mass is 80 kg on the earth's surface is in a spacecraft at a height of 2 earth radii above the earth's surface His weight there is?

Answer 1

20kg

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Another contributor jumped in:

The man's mass doesn't change. He carries 50 kg with him wherever he goes.

But his weight changes, depending on the acceleration of gravity where he is.

Weight = (mass) times (acceleration of gravity).

So we need to find the acceleration of gravity at 2 radii above the surface.

The acceleration of gravity is proportional to the square of the distance from the

place to the center of the earth, and on the surface, it's 9.8 m/s2 .

On the surface, you're 1 radius from the center. At 2 radii from the surface, you're

2 more radii from the center, or 3 radii all together. So your distance from the center

has tripled.

The acceleration of gravity is 1/32 of its original value, or 1/9th of 9.8 .

9.8/9 = 1.089 m/s2 at that position in space.

The man's weight is (mass) times (acceleration of gravity).

On the surface, he weighs (50 x 9.8) = 490 newtons (110.2 pounds).

Out there at 3 radii from the center, he weighs (50 x 1.089) = 54.4 newtons (12.25 pounds).