physics question

Question

An astronaut in an orbiting spacecraft feels "weightless" because she

Answer 1

An astronaut in an orbiting spacecraft feels "weightlessness" because the astronaut and the spacecraft have the same acceleration - the acceleration of gravitational attraction from the planet. The only force that acts on the astronaut in this case - is the force of gravity.

Frankly speaking, we must talk not about the weight, but about apparent wait in this situation. Let me remind you that weight (force of gravity) - is the force of gravitational attraction from the Earth. You all know the formula for it

W = mg

The direction of this force is vertically down and this force is applied to the body. This force is gravitational in nature. As the result the body acts on the surface where it is at rest or on the scale. This force we call apparent weight. It is applied not to the body, but to the surface or scale. The nature of this force is electromagnetic.

Now what about the magnitude of weight and apparent weigh?

Mass of the body is a constant that never changes. Acceleration of free fall g at a given location is the same for all bodies, hence, weight of the body at a given point is constant.

You must remember that acceleration of free fall could be found by the use of formula

g = G M / (R + h )²,

where

G = 6.67 x 10 ^{- 11} Nkg²/ m² - gravitational constant,

R - radius of the planet,

h - altitude above the surface of the planet.

Apparent way could vary. It depends whether the body is on horizontal surface or not. Whether the body moves with acceleration or not.

In case of orbiting the planet on board of spacecraft, the body is not exerting force on the support surface, because they all move with the same acceleration g due to gravity. The normal force acting on the body is 0! As a result - the apparent weight of the body is also 0 (Newton's third law). And astronaut experience "weightlessness"