Question

Why does an astronomer experience weightlessness in outer space?
A).No gravitational force acts on him
B).No frictional force acts on him
C).There is no air resistance in outer space
D).There is a vacuum in outer pace

Answer 1

Hint: We experience weight when the ground that we stand on applies a force in the opposite direction to the gravitational pull, that is pulling us to the ground. Weight is relative, it depends upon where the person is standing.

Complete Step By Step Answer:
The orbital motion of the astronauts inside a spaceship or space station creates a "weightless" environment. If the only force operating on a human is gravity, that person feels weightless.
For instance Standing on a building would result in two forces acting on you: gravity pulling you down and the building pushing you up. That is how we experience weight.
There is no net external gravitational force acting on a body in outer space. As we know, gravitational force constantly acts on any object, but when we go close to the planet, its force dominates; nevertheless, when a body is in space, the net gravitational force of all the bodies is balanced, and the net force is zero.
The correct answer is option A, No gravitational force acts on him.

Note:
Falling is another instance where we experience weightlessness. This is because there is no ground to provide the normal force. Also weight is relative. That is, the weight of a person will be greater at the poles than at the equator.