(Center of Gravity)?

Question

When an astronaut spins when doing acrobatic aboard an orbiting space vehicle, what point does the body spin about?

Answer 1

his center of gravity. he still has one, because he is still under the force of gravity, it's just that the force of gravity is significantly less in space than it is on earth.

Answer 2

A spin is by definition angular motion around an axis reference point on the body in motion. So the spin's velocity and acceleration vectors are relative to the body that is spinning.

Through some fancy math, called vector analysis, we can write the velocity and acceleration vectors relative to any other reference framework...like the center of the Earth, axis of the space ship, or center of the universe. The motion would still be a spin, but the new equations would simply be a translation of the original spin vectors relative to the spinning astronaut. We often do these translations to make solving the equations easier.

By comparison, the term rotation is a more general term describing angular motion. Thus, we can say, the astronaut is rotating around her own axis (in which case the rotation is a spin because the reference point is on the body in motion). Or we can say the space ship is rotating around the Earth's center (in which case the rotation is a revolution because the reference point is outside the body in motion).

Answer 3

The astronaut spins about an axis passing through his center of mass. Keep in mind, the astronaut's center of mass can move around a little based on the orientation of his limbs.

Answer 4

I would think that it would be the center of the astronaut's mass. You could say that was the center of gravity, however, at the size of an astronaut gravity is incredibly small.

Answer 5

The question is about astronaut in a spinning space vehicle. We may require the space craft to spin for the purpose of stability. [A bullet out of a rifle is spinning and it gets its stability due to spin and does not topple]. It is not necessary for the astronaut to spin along with the space craft. Our body is not used to spinning. Pilot in a fighter aircraft when subject to tight "g" in a loop has problems of getting unconscious. due to either excessive supply of blood to brain or total loss of blood supply to brain. These situations have to be avoided. Normally an astronaut has to be fastened to space vehicle when it is turning or spinning or maneuvering. Thus he is immobilized to avoid injuries and other problems as above. His body therefore spins with the space vehicle as one unit.

Answer 6

Around the center of mass. If there is gravity present, the center of mass would be what you are calling the center of gravity. It should really be referred to as the center of mass.